Explore Related Concepts

Application of Multiple Reflection of Sound

Application of multiple reflection of sound is a useful to understand the reflection of sound along with its application. The basics laws are governed for understanding the complete application of multiple reflection of sound.  This concept is almost similar to that of the reflection of light.

Like light ray reflected, in the similar way, the waves of sound also get reflected.  So the bouncing back or the reflection of the sound wave from the surface of liquid or solid is known as reflection of sound. Like light waves follow laws of reflection, in the similar way the sound wave also follows the same. So in this case, the angle of incidence of sound wave is equal to the angle of reflection of sound wave. But only important point here is that the sound wave needs rough or polished and large obstacle is very much necessary.

Above discussion is basic about the reflection of sound. Now we need to understand the multiple reflection of sound. This is similar with reflection of sound but it is multiple reflections that are more than one reflection.  This phenomenon has been used in various applications and all applications are of great use.  Application of multiple reflection of sound has been used in every field and this can be better understood by taking some practical examples. The same examples are described in the next paragraph for understanding purpose.

Multiple reflection of sound is used in various appliances and devices.  The examples are as follows: 

1) Loudspeaker
2) Hearing aid
3) Megaphone
4) Sound board,
5) Stethoscope etc.

The above five applications are the general applications in the present life. To understand the multiple reflection phenomenon’s, let us discuss application of multiple reflection of sound in an elaborative way.

The appliances such as bulb born, loudspeakers, and megaphones, all are utilized to send or transmit the sound in the required or we can say desired direction.  All these devices work basically on the laws of the reflection of the sound waves. These types of devices generally use a funnel like conical tube. At the narrow of the tube, the sound is introduced and finally makes it to come at the wider end.  And because of the multiple reflection, the amplitude of sound rises up, which actually makes the sound louder. Even the name of loudspeaker is also given with respect to its use.

Stethoscope used by doctors, which is actually used to hear the integral organ sounds of the patient. This is basically used for the diagnostic purposes.  It also works on the same principle of multiple laws of reflection.   In this case, actually sound is first received by the chest piece and then it is sent to ear piece by undergoing multiple reflections through a long tube. The doctor generally hears in his ears for the basic diagnostic purpose of the patient.

All other appliances work on the same principle.  Only thing to understand the all such appliances, we need to focus first on the basic concepts of the reflection as well as the multiple reflection.  Once we have the thorough knowledge of the same one can understand any appliance based on multiple reflection principle. So this was all about application of multiple reflection of sound.

Best Results From Wikipedia Yahoo Answers Youtube


From Wikipedia

Sound effect

For the album by The Jam, seeSound Affects.

Sound effects or audio effects are artificially created or enhanced sounds, or sound processes used to emphasize artistic or other content of films, television shows, live performance, animation, video games, music, or other media. In motion picture and television production, a sound effect is a sound recorded and presented to make a specific storytelling or creative point without the use of dialogue or music. The term often refers to a process applied to a recording, without necessarily referring to the recording itself. In professional motion picture and television production, dialogue, music, and sound effects recordings are treated as separate elements. Dialogue and music recordings are never referred to as sound effects, even though the processes applied to them, such as reverberation or flanging effects, often are called "sound effects".

Film

In the context of motion pictures and television, sound effects refers to an entire hierarchy of sound elements, whose production encompasses many different disciplines, including:

  • Hard sound effects are common sounds that appear on screen, such as door slams, weapons firing, and cars driving by.
  • Background (or BG) sound effects are sounds that do not explicitly synchronize with the picture, but indicate setting to the audience, such as forest sounds, the buzzing of fluorescent lights, and car interiors. The sound of people talking in the background is also considered a "BG," but only if the speaker is unintelligible and the language is unrecognizable (this is known as walla). These background noises are also called ambience or atmos ("atmosphere").
  • Foley sound effects are sounds that synchronize on screen, and require the expertise of a Foley artist to record properly. Footsteps, the movement of hand props (e.g., a tea cup and saucer), and the rustling of cloth are common foley units.
  • Design sound effects are sounds that do not normally occur in nature, or are impossible to record in nature. These sounds are used to suggest futuristic technology in a science fiction film, or are used in a musical fashion to create an emotional mood.

Each of these sound effect categories is specialized, with sound editors known as specialists in an area of sound effects (e.g. a "Car cutter" or "Guns cutter").

The process can be separated into two steps: the recording of the effects, and the processing. Sound effects are often custom recorded for each project, but to save time and money a recording may be taken from a library of stock sound effects (such as the famous Wilhelm scream). A sound effect library might contain every effect a producer requires, yet the timing and aesthetics of a tailor-made sound are often preferred.

Foley is another method of adding sound effects. Foley is more of a technique for creating sound effects than a type of sound effect, but it is often used for creating the incidental real world sounds that are very specific to what is going on onscreen, such as footsteps. With this technique the action onscreen is essentially recreated in order to try and match it as closely as possible. If done correctly it is very hard for audiences to tell what sounds were added and what sounds were originally recorded (location sound).

In the early days of film and radio, Foley artists would add sounds in realtime or pre-recorded sound effects would be played back from analogue discs in realtime (while watching the picture). Today, with effects held in digital format, it is easy to create any required sequence to be played in any desired timeline.

Video games

The principles involved with modern video game sound effects (since the introduction of sample playback) are essentially the same as those of motion pictures. Typically a game project requires two jobs to be completed: sounds must be recorded or selected from a library and a sound engine must be programmed so that those sounds can be incorporated into the game's interactive environment.

In earlier computers and video game systems, sound effects were typically produced using sound synthesis. In modern systems, the increases in storage capacity and playback quality has allowed sampled sound to be used. The modern systems also frequently utilize positional audio, often with hardware acceleration, and real-time audio post-processing, which can also be tied to the 3D graphics development. Based on the internal state of the game, multiple different calculations can be made. This will allow for, for example, realistic sound dampening, echoes and doppler effect.

Historically the simplicity of game environments reduced the required number of sounds needed, and thus only one or two people were directly responsible for the sound recording and design. As the video game business has grown and computer sound reproduction quality has increased, however, the team of sound designers dedicated to game projects has likewise grown and the demands placed on them may now approach those of mid-budget motion pictures.

Music

Some pieces of music use sound effects that are made by a music instrument or by other means. An early example is 18th century Toy Symphony. Richard Wagner in the opera Das Rheingold (1869) lets a choir of anvils introduce the scene of the dwarfs who have to work in the mines, similar to the introduction of the dwarfs in the 1937 Disney movie Snow White. Klaus Doldingers soundtrack for the 1981 movie Das Boot includes a title score with an sonar sound to reflect the U-boat setting.

Recording

The most realistic sound effects originate from original sources; the closest sound to machine-gun fire that we can replay is an original recording of actual machine guns. Less realistic sound effects are digitally synthesized

Sound reinforcement system

A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience. In some situations, a sound reinforcement system is also used to enhance the sound of the sources on the stage, as opposed to simply amplifying the sources unaltered. A sound reinforcement system may be very complex, including hundreds of microphones, complex mixing and signal processing systems, tens of thousands of watts of amplification, and multiple loudspeaker arrays, all overseen by a team of audio engineers and technicians. On the other hand, a sound reinforcement system can be as simple as a small PA system in a coffeehouse, consisting of a single microphone connected to a self-powered 100-watt loudspeaker system. In both cases, these systems reinforce sound to make it louder or distribute it to a wider audience.

Some audio engineers and other sound industry professionals disagree over whether these audio systems should be called sound reinforcement (SR) systems or public address (PA) systems. Distinguishing between the two terms by technology and capability is common, while others distinguish by intended use (e.g., SR systems are for live music and PA systems are for reproduction of speech and recorded music in buildings and institutions). In some regions or markets, the distinction between the two terms is important, though the terms are considered interchangeable in many professional circles.

Basic concept

A typical sound reinforcement system consists of; inputtransducers (e.g., microphones), which convert sound energy into an electric signal,signal processorswhich alter the signal characteristics,amplifiers, which add power to the signal without otherwise changing its content, and output transducers (e.g., loudspeakers) , which convert the signal back into sound energy. These primary parts involve varying amounts of individual components to achieve the desired goal of reinforcing and clarifying the sound to the audience, performers, or other individuals.

Signal path

Sound reinforcement in a large format system typically involves a signal path that starts with an instrument pickup or a microphone (transducer) which is plugged into a multicore cable (often called a "snake"). The snake then routes the signals of all of the inputs to the Front of the House (FOH) and Monitor consoles. Once the signal is at a channel on the console, this signal can be equalized, compressed, or panned before being routed to an output bus. The signal may also be routed into an external effects processor, which outputs a wet (effected) version of the signal, which is typically mixed in varying amounts with the dry (ineffected) signal.

The signal is then routed to a bus, also known as a mix group, subgroup or simply 'group'. A group of signals may be routed through an additional bus before being sent to the main bus to allow the engineer to control the levels of several related signals at once. For example, all of the different microphones for a drum set might be sent to their own bus so that the volume of the entire drum set sound can be controlled with a single fader or a pair of faders. A bus can often be processed just like an individual input channel, allowing the engineer to process a whole group of signals at once. The signal is then typically routed with everything else to the stereo masters on a console. Mixing consoles also have additional sends, also referred to as auxes, on each input channel so that a different mix can be created and sent elsewhere.

The next step in the signal path generally depends on the size of the system in place. In smaller systems, the main outputs are often sent to an additional equalizer, or directly to a power amplifier, with one or more loudspeakers (typically two) then connected to that amplifier. In large-format systems, the signal is typically first routed through an equalizer then to a crossover. A crossover splits the signal into multiple frequency bands with each band being sent to separate amplifiers and speaker enclosures for low, middle, and high-frequency signals. Low-frequency sounds are sent to subwoofers, and middle and high-frequency sounds are typically sent to full-range speaker cabinets.

System components

Input transducers

Many types of input transducers can be found in a sound reinforcement system, with microphones being the most commonly used input device. They can be classified according to their method of transduction, pickup (or polar) pattern or their functional application. Most microphones used in sound reinforcement are either dynamic or condenser microphones.

Microphones used for sound reinforcement are positioned and mounted in many ways, including base-weighted upright stands, podium mounts, tie-clips, instrument mounts, and headset mounts. Headset mounted and tie-clip mounted microphones are often used with wireless transmission to allow performers or speakers to move freely. Early adopters of headset mounted microphones technology included country singer Garth Brooks, Kate Bush, and Madonna.

There are many other types of input transducers which may be used occasionally, including magnetic pickups used in electric guitars and electric basses, contact microphones used on stringed instruments, and piano and phonograph pickups (cartridges) used in rec

Prism (optics)

In optics, a prism is a transparent optical element with flat, polished surfaces that refractlight. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use "prism" usually refers to this type. Some types of optical prism are not in fact in the shape of geometric prisms. Prisms are typically made out of glass, but can be made from any material that is transparent to the wavelengths for which they are designed.

A prism can be used to break light up into its constituent spectralcolors (the colors of the rainbow). Prisms can also be used to reflect light, or to split light into components with different polarizations.

How prisms work

Light changes speed as it moves from one medium to another (for example, from air into the glass of the prism). This speed change causes the light to be refracted and to enter the new medium at a different angle (Huygens principle). The degree of bending of the light's path depends on the angle that the incident beam of light makes with the surface, and on the ratio between the refractive indices of the two media (Snell's law). The refractive index of many materials (such as glass) varies with the wavelength or color of the light used, a phenomenon known as dispersion. This causes light of different colors to be refracted differently and to leave the prism at different angles, creating an effect similar to arainbow. This can be used to separate a beam of white light into its constituent spectrum of colors. Prisms will generally disperse light over a much larger frequency bandwidth than diffraction gratings, making them useful for broad-spectrum spectroscopy. Furthermore, prisms do not suffer from complications arising from overlapping spectral orders, which all gratings have.

Prisms are sometimes used for the internal reflection at the surfaces rather than for dispersion. If light inside the prism hits one of the surfaces at a sufficiently steep angle, total internal reflection occurs and all of the light is reflected. This makes a prism a useful substitute for a mirror in some situations.

Deviation angle and dispersion

Ray angle deviation and dispersion through a prism can be determined by tracing a sample ray through the element and using Snell's law at each interface. The exact expressions for prism deviation and dispersion are complex, but for small angle of incidence \theta_0 and small angle \alpha they can be approximated to give a simple formula. For the prism shown at right, the indicated angles are given by

\begin{align}

\theta'_0 &\approx \frac{n_0}{n_1} \theta_0 \\ \theta_1 &= \alpha - \theta'_0 \\ \theta'_1 &\approx \frac{n_1}{n_2} \theta_1 \\ \theta_2 &= \theta'_1 - \alpha \end{align}. For a prism in air n_0=n_2 \simeq 1. Defining n=n_1, the deviation angle \delta is given by

{\delta = \theta_2 + \theta_0 \approx n \theta_1 - \alpha + \theta_0 = n \alpha - n \theta'_0 - \alpha + \theta_0 \approx (n - 1) \alpha}

The dispersion \delta (\lambda) is the wavelength-dependent deviation angle of the prism, so that for a thin prism the dispersion is given by

\delta (\lambda) \approx [ n (\lambda) - 1 ] \alpha

Prisms and the nature of light

In Isaac Newton's time, it was believed that white light was colorless, and that the prism itself produced the color. Newton's experiments convinced him that all the colors already existed in the light in a heterogeneous fashion, and that "corpuscles" (particles) of light were fanned out because particles with different colors traveled with different speeds through the prism. It was only later that Young and Fresnel combined Newton's particle theory with Huygen's wave theory to show that color is the visible manifestation of light's wavelength.

Newton arrived at his conclusion by passing the red color from one prism through a second prism and found the color unchanged. From this, he concluded that the colors must already be present in the incoming light — thus, the prism did not create colors, but merely separated colors that are already there. He also used a lens and a second prism to recompose the spectrum back into white light. This experiment has become a classic example of the methodology introduced during the scientific revolution. The results of this experiment dramatically transformed the field of metaphysics, leading to John Locke's primary vs secondary quality distinction.

Newton discussed prism dispersion in great detail in his book Opticks. He also introduced the use of more than one prism to control dispersion. Newton's description of his experiments on prism dispersion was qualitative, and is quite readable. A quantitative description ofmultiple-prism dispersion was not needed until multiple prism laser beam expanders were introduced in the 1980s.

Scattering

Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections that undergo scattering are often called diffuse reflections and unscattered reflections are calledspecular(mirror-like) reflections.

The types of non-uniformities which can cause scattering, sometimes known as scatterers or scattering centers, are too numerous to list, but a small sample includes particles, bubbles, droplets, density fluctuations in fluids, crystallites in polycrystalline solids, defects in monocrystalline solids, surface roughness, cells in organisms, and textile fibers in clothing. The effects of such features on the path of almost any type of propagating wave or moving particle can be described in the framework of scattering theory.

Some areas where scattering and scattering theory are significant include radar sensing, medical ultrasound, semiconductor wafer inspection, polymerization process monitoring, acoustic tiling, free-space communications, and computer-generated imagery.

Single and multiple scattering

When radiation is only scattered by one localized scattering center, this is called single scattering. It is very common that scattering centers are grouped together, and in those cases the radiation may scatter many times, which is known as multiple scattering. The main difference between the effects of single and multiple scattering is that single scattering can usually be treated as a random phenomenon and multiple scattering is usually more deterministic. Because the location of a single scattering center is not usually well known relative to the path of the radiation, the outcome, which tends to depend strongly on the exact incoming trajectory, appears random to an observer. This type of scattering would be exemplified by an electron being fired at an atomic nucleus. In that case, the atom's exact position relative to the path of the electron is unknown and would be immeasurable, so the exact direction of the electron after the collision is unknown, plus the quantum-mechanical nature of this particular interaction also makes the interaction random. Single scattering is therefore often described by probability distributions.

With multiple scattering, the randomness of the interaction tends to be averaged out by the large number of scattering events, so that the final path of the radiation appears to be a deterministic distribution of intensity. This is exemplified by a light beam passing through thick fog. Multiple scattering is highly analogous to diffusion, and the terms multiple scattering and diffusion are interchangeable in many contexts. Optical elements designed to produce multiple scattering are thus known as diffusers. Coherent backscattering, an enhancement of backscattering that occurs when coherent radiation is multiply scattered by a random medium, is usually attributed to weak localization.

Not all single scattering is random, however. A well-controlled laser beam can be exactly positioned to scatter off a microscopic particle with a deterministic outcome, for instance. Such situations are encountered in radar scattering as well, where the targets tend to be macroscopic objects such as people or aircraft.

Similarly, multiple scattering can sometimes have somewhat random outcomes, particularly with coherent radiation. The random fluctuations in the multiply-scattered intensity of coherent radiation are called speckles. Speckle also occurs if multiple parts of a coherent wave scatter from different centers. In certain rare circumstances, multiple scattering may only involve small number of interactions such that the randomness is not completely averaged out. These systems are considered to be some of the most difficult to model accurately.

The description of scattering and the distinction between single and multiple scattering are often highly involved with wave-particle duality.

Scattering theory

Major research problems in scattering often involve predicting how various systems will scatter radiation, which can almost always be solved given sufficient computing power and knowledge of the system. A widely studied but more difficult challenge is the inverse scattering problem, in which the goal is to observe scattered radiation and use that observation to determine properties of either the scatterer or the radiation before scattering. In general, the inverse is not unique; several different types of scattering centers can usually give rise to the same pattern of scattered radiation, so the problem is not solvable in the general case. Fortunately, there are ways to extract some useful, albeit incomplete, information about the scatterer, and these techniques are widely used for sensing and metrology applications (Colton & Kress 1998).

Electromagnetic scattering

Electromagnetic waves are one of the best known and most commonly encountered forms of radiation that undergo scattering. Scattering of light and radio waves (especially in radar) is particularly important. Several different aspects of electromagnetic scattering are distinct enough to have conventional names. Major forms of elastic light scattering (involving negligible energy transfer) are Rayleigh scattering and Mie scattering. Inelastic scattering includes Brillouin scattering, Raman scattering, inelastic X-ray


From Yahoo Answers

Question:As far as my requirement is concerned I would like it in detail please.

Answers:The below is from a slide presentation on authorstream.com. <- I did not change any of the spelling, which, as you will notice, is not the best. The web address is below, in sources. If you go to the slide presentation, go to the very last slide, where they show several related presentations that you can click on and view. The website does not cost, so enjoy and learn. Slide 5 Uses of multiple reflection Megaphones or loudhailers, horns, musical instrument, such as trumpets and shehanais, are all designed to send sound in a particular direction without spreading it in all direction. In these instruments, a tube followed by a conical openings reflects sound successively to guide most of the sound waves from the source in the forward direction towards audience. Stethoscope is a medical instrument used for listening to sounds produced within the body. In Stethoscope the sound of the patient s heartbeat reaches the doctor s ears buy multiple reflection of sound. I hope this is helpful. You might want to run a search for "multiple reflection of sound" on different search engines and see is anything else comes up for you. Good luck.

Question:Sorry if this seems confusing, but I need help with a math project. We are doing applications of trigonometric graphs and I am doing mine on acoustics. I will need to know how the waves change (in terms of amplitude, wavelengths, etc.) when they are reflected and what this does to the sound itself. If you could provide sources as well, I would appreciate that. Finally, if there are any graphs that you could show me to help explain this, I would appreciate that as well (I am a visual learner!) P.S: I need layman's terms! (:

Answers:The wave changes to a closer wavelength as it bottles up before it bounces it also diminishes due to absorption from the medium it is bouncing off. Softer material will absorb more sound then dense. Put different materials in front of a speaker and you will be able toexperiencee the changes and may help youdescribee them in better terms of your own words. Your ears are capable of distinguishing thedifferencess you just have to look for them. What a betterexperimentt then blasting yourFavoritt music?

Question:When an object is forced to vibrate at its natural frequency, its vibration amplitude increases. True or false? Which of the following would be most likely to transmit sound the best? a. Water in a swimming pool b. Water in the ocean c. Air in you classroom d. Steel in a bridge The speed of sound in dry air at 20 degrees Celsius is 340 m/s. How far away is a jet plane when you notice a 2-second delay between seeing the plane and hearing it? a. 6800 m. b. 680 m. c. 3430 m. d. 40 m. If the sounding board were left out of a music box, the music box would a. sound the same as usual. b. not sound at all. c. make little "plinks" that you could hardly hear. Resonance occurs when a. sound makes multiple reflections. b. sound changes speed going from one medium to another. c. the amplitude of a wave is amplified. d. an object is forced to vibrate at its natural frequency. Beats can be heard when two tuning forks a. are sounded together. b. have the same frequency and are sounded together. c. have almost the same frequency and are sounded together. d. all of the above e. none of the above You note a 2-second delay for an echo in a canyon. What is the distance to the wall of the canyon? Ten violins produce a sound intensity level of 50 dB in a concert hall. How many violins are needed to produce a level of 60 dB?

Answers:You haven't studied the material, yes? Answering these questions for you will help your grade but it will not help you learn anything. Only you can do that by your own efforts. Nor will your grade reflect what you actually know. Consequently, I do not wish to take part in your effort to cheat yourself out of an education. Sorry. That's on you.

Question:Help! Physics! Yuck! I have an exam next week on this optics and lenses stuff and our teacher gave us a sample Multiple Choice paper to work through......... I got about 80% of them but I can't figure out the answers for these ones. Can you help? Thanks! p.s. I don't need the whole method and how to work out the whole question lol I still need a challenge :)! I'd like to try and get them myself but sometimes I find it easier to work out the method going backwards from the answer if you get me! I just really don't get these ones. Maybe you can give me the answer i'm aiming for and clue of the method to get me going? If I'm really stuck I'll post the ones I still don't understand later and maybe ask for a bit more help! thnx guys xxxxxx :) stacey x ps even if you can just help with one of them thats fine! ok so here's the questions A patient's eye has an optical power of 63 dioptres. The patient wears glasses of power -7 dioptres. What is the combined optical power of the eye and glasses? a.5.7 dioptres b.56 dioptres c.70 dioptres d.6.3 dioptres An object is placed 20 cm from a lens with a positive focal length of 5 cm. What is the separation of the image position from the lens? a.Greater than 10m on the opposite side of the lens from the object b.20 cm on the opposite side of the lens from the object c.7 cm on the opposite side of the lens from the object d.7 cm on the same side of the lens as the object A string vibrates with a fundamental frequency of 400Hz. What is the wavelength of the sound emitted? Take the speed of sound to be 340m/s. a.1.18 cm b.1.4 m c.0.85 m d.0.25 cm What is the wavelength of light in the vitreous humour of the eye, where the wavelength of the light is 0.64 m in air? Take the refractive index of the vitreous humour to be 1.3 and the refractive index of air to be that of a vacuum. a.0.64 m b.0.49 m c.1.94 m d.0.83 m A lens has one convex radius of curvature of 0.2 m and one concave radius of curvature of 0.4 m for the two surfaces. What is the focal length of the lens? Take the lens refractive index to be 1.5. a.0.27 m b.0.6 m c.-0.8 m d.0.8 m How many of the following statements are correct? i) In reflection, the angle of incidence is equal to the angle of reflection ii) A specular reflection occurs at a rough surface iii) Two mirrors placed at right angles to each other can return a light ray to be parallel to its original direction iv) A reflection can occur at an interface between differing refractive indices. a.1 statement b.4 statements c.2 statements d.3 statements A fly of length 4 mm is illuminated with a spot light and a magnifying glass is positioned 5 cm from the fly. An image screen is placed on the other side of the lens at a separation of 30 cm from the lens. How long is the image of the fly on the screen? 37.5 mm 20 mm 24 mm 0.7 mm A glass plate with a refractive index of 1.5 is inserted in to a beam such that the angle of incidence is 30 degrees from the normal of the plate. Through what angle is the ray inside the plate deviated from that of the incident ray? a.0 degrees b.10.5 degrees c.19.5 degrees d.30 degrees A glass plate is inserted in to a beam such that the angle of incidence is 30 degrees from the normal of the plate. Through what angle is the ray that is transmitted through the glass plate deviated from that of the incident ray? Take the plate to have parallel surfaces and a refractive index of 1.5. a.15 degrees b.0 degrees c.30 degrees d.50 degrees Light in a refractive index 1.5 is incident at an interface with air of refractive index 1. For total internal reflection, what is the minimum angle of incidence relative to the normal at the interface i.e., the critical angle? a.34 degrees b.48 degrees c.20 degrees d.42 degrees If the sound intensity level of one person speaking is 50dB, what is the sound intensity level where 4 people are speaking? a.200 b.50 c.56 d.90 An ultrasound echo from the midline of the brain is detected back at the ultrasound instrument 0.1 miliseconds after the source pulse is emitted from the same instrument. How far from the source is the midline? Assume that the speed of sound in the brain tissue is 1540m/s. a.7.7 cm b.15.4 cm c.30.8 cm d.30.8 mm What focal length is given by the cornea? For your calculation, take the radius of curvature of the cornea to be 7.0 mm and approximate the cornea to act as a lens in air with one side curved and the other side plane. Take the refractive index of the cornea to be 1.40. a.0.2 mm b.5.0 mm c.6.0 mm d.17.5 mm

Answers:Q1. None of the answers are correct. The teacher is probably looking for answer b as you can generally add lens powers (reciprical of focal length). However, this is only true for thin lenses in contact. In this case the eye lens and spectacle lens are both thick and seperated. Q2. Use the lens equation 1/u + 1/v = 1/f If you don't recognize this then you are in real trouble Q3. Use the formula frequency x wavelength = speed. Make sure all your values are in the same units. Q4. Frequency x wavelength = speed As the frequency is constant then you can calculate the different wavelength knowing how the speed changes. Speed in medium = speed in air(vacuum) / n Q5. Power of a thin lens k = (n-1)(c1 - c2) where c1 and c2 are the surface curvatures. (Note that the signs are opposite for each side of a convex lens.) Focal length = 1/k Q6. All are true except ii That's enough for now.

From Youtube

LS-2 Line Selector [BOSS Sound Check] :The LS-2 Line Selector makes it easy to switch settings among several effects and to route input and output signals. Two line loops and six looping modes provide a wide variety of applications. Used with an AC adaptor, the LS-2 can also supply 9V DC power to several BOSS compact pedals. This makes it an ideal power supply and master switching unit for multiple effects setups.

Precomputed Wave Simulation for Real-time Sound Propagation of Dynamic Sources in Complex Scenes :We present a method for real-time sound propagation that captures all wave effects, including diffraction and reverberation, for multiple moving sources and a moving listener in a complex, static 3D scene. It performs an offline numerical simulation over the scene and then applies a novel technique to extract and compactly encode the perceptually salient information in the resulting acoustic responses. Each response is automatically broken into two phases: early reflections (ER) and late reverberation (LR), via a threshold on the temporal density of arriving wavefronts. The LR is simulated and stored in the frequency domain, once per room in the scene. The ER accounts for more detailed spatial variation, by recording a set of peak delays/amplitudes in the time domain and a residual frequency response sampled in octave frequency bands, at each source/receiver point pair in a 5D grid. An efficient run-time uses this precomputed representation to perform binaural sound rendering based on frequency-domain convolution. Our system demonstrates realistic, wave-based acoustic effects in real time, including diffraction low-passing behind obstructions, sound focusing, hollow reverberation in empty rooms, sound diffusion in fully-furnished rooms, and realistic late reverberation [Nikunj Raghuvanshi, John Snyder, Ravish Mehra, Ming C. Lin, Naga Govindaraju]. gamma.cs.unc.edu