What is Sound: Definition and 1000 Discussions

In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, sound is the reception of such waves and their perception by the brain. Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In air at atmospheric pressure, these represent sound waves with wavelengths of 17 meters (56 ft) to 1.7 centimetres (0.67 in). Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges.

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  1. R

    Why is there no SI unit for sound?

    The deciBel is probably the most commonly used unit for sound, but why isn't there an SI unit? Also, what is a logarithmic unit? Thanks.
  2. H

    Why amplitude doesn't affect speed of sound?

    If amplitude is the measure of energy in a sound wave - On increasing amplitude, the medium particles should hit each other in lesser time because they have more force(which increases their speed) and this cycle should repeat and repeat. Eventually, the speed of sound should increase. But...
  3. A

    Modelling the sound of a drum head.

    Please excuse me if this is not the most appropriate subforum for this question and please move it if necessary. I am trying to make a numerical model with Mathematica to synthesize the sound of a struck drum head (circular membrane). I solve the wave equation for a circular membrane to get a...
  4. J

    Sound Defraction in a medium

    Homework Statement the laws of refraction and reflection are the same for sound as for light. the speed of sound is 340 m/s in air and 1510 m/s in water. if a sound wave traveling in air approaches a plane water surface at an angle of incidence 12°, what is the angle of refraction? Homework...
  5. D

    C/C++ How to read an electric signal through sound card? (C++)

    How to read a signal through the sound card? I want to capture an amplified electric signal that emerge in the heart, and then to draw the ECG diagram. Can I use the soundcard's jacks for this purpose? if then, what is the best method to use to capture these signals using C++ on windows...
  6. C

    Why is sound different in lower temperatures

    I am the least of a 'physics' person yet I find myself here, It is very cold just now in eastern Poland. for a week -20C - 4F very sunny and dry Why do the nearby church bells (100 meters?) certainly have a different sound/higher tone to my ears at least now in these low dry high pressure...
  7. A

    Certification of Sound Level Meter (Not calibration)

    Hi, I would like to know if anyone knows where can I find people who do certification of Sound Level Meter (Not calibration). I need to certify my Sound Level Meter to IEC 61672. Please provide details if you know who can do it. Thank you. Best Regards, Richard
  8. J

    Sound of overhead plane is heard in the distance

    Homework Statement A jet is flying horizontally [drawing shows an observer on the ground, a plane overhead at point B, and an outline of the plane from it's observed position to the left at point A. The angle between the observer and point A is 36°.] When the plane is directly overhead at B, a...
  9. L

    In order to achieve beam forming of the sound waves

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  10. J

    Find the distance between objects and sound source

    Homework Statement One microphone is located at the origin, and a second microphone is located on the +y-axis. The microphones are separated by a distance of D= 1.21m. A source of sound is located on the +x-axis, its distance from microphones 1 and 2 being L1 and L2, respectively. The speed of...
  11. I

    Acoustic ceiling effectiveness in reducing sound

    I am considering applying spray-on acoustic/popcorn ceilings to reduce the noise level in my house. I haven't found any data supporting that popcorn ceiling reduce noise level. I am looking for data, physics, experiments, and tools to help me figure this out. I asked this question at...
  12. J

    How many machines can a factory add before exceeding the 90-dB limit?

    Homework Statement a noisy machine in a factory produces a decibel rating of 80 dB. how manyidentical machines could you add to the factory without exceeding the 90-dB limit? Homework Equations I=P/A and B+10log(I/I(sub)0) ... (I think) The Attempt at a Solution I tried to find...
  13. P

    Fourier Transform of an equation representing a sound

    Homework Statement http://dl.dropbox.com/u/11341635/IntegrationProblem.jpg Homework Equations http://dl.dropbox.com/u/11341635/Fourier%20Transform%20Equations.jpg The Attempt at a Solution http://dl.dropbox.com/u/11341635/1st%20part%20of%20attempt.png...
  14. genxium

    Understanding Sound Cavity: A Guide for Greenhands

    Homework Statement No specific question, I'm a greenhand to waves, so when it came to sound cavity, I was just confused how the teacher(in the video lecture,I'm not a physics major) can distinguish which side is a node and which is an anti-node, it seems too fast for me, could anyone give me a...
  15. A

    Waves and sounds, finding the speed of a jet using the speed of sound

    Homework Statement A jet is flying horizontally, as the drawing shows. When the plane is directly overhead at B, a person on the ground hears the sound coming from A in the drawing. The average temperature of the air is 20 oC. If the speed of the plane at A is 180 m/s, what is its speed at...
  16. O

    Can the shape and amount of water in a glass affect the sound it produces?

    I'm doing a project on a water xylophone, and I have a couple questions about it. Please site your sources because we need all the help we can get. Thanks =D 1) How does the shape of the glass affect the sound the water produces. 2) Why does more water in a glass lower the frequency of the...
  17. D

    Sound Intensity Level and Hearing Problem

    Thank you for the help!
  18. F

    Dimensional analysis (Speed of sound)

    Speed of sound The speed of sound c in a gas depends on among other things on the pressure on the gas, the density and probably, possibly on their viscosity. Determine c- My Variable list: Pressure p ML^-1T^-2 Density ρ ML^-3 Speed v LT^-1 My matrix: | | M | L | T | | p | 1 |...
  19. V

    What will speed of sound for sourse and observer if both are moving wrt air?

    wrt means with respect to Homework Statement see attachment that contains full question. firstly read paragraph then see on question. The Attempt at a Solution velocity of sound will be 340ms-1 wrt air or ground(since air i snot blowng). Now speed of soud wrt train A= speed of sound...
  20. K

    A submarine sonar system sends a burst of sound with a frequency of

    A submarine sonar system sends a burst of sound with a frequency of 325Hz. The sound wave bounces off an underwater rock face and returns to the submarine in 8.50s. If the wavelength of the sound is 4.71m, how far away is the rock face? (Ans: 6.51km ) -- v=fλ λ=wavelength f=frequency...
  21. F

    Digital audio from a sound card

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  22. A

    Possible to break a glass if you emit a loud sound?

    Knowing that its possible to break a glass if you emit a loud sound at its resonant frequency. If you do the same for Human skulls, there will not only be a sound sleep, but a sound death too. Is that possible?
  23. S

    Sound waves to test for faults in girders

    hi i have a physics questions about sound Sound waves are used to detect faults in girders. a cro is used to detect these faults, a pulse producer and a detector is placed on opposite sides of the detector. The safe detector has a upwards spike at 0microseconds and at 10 microseconds. The...
  24. S

    How sound waves detect faults in girders

    [PLAIN]http://postimage.org/image/4ure9j3sr/1. Homework Statement i have a physics questions about sound Sound waves are used to detect faults in girders. a cro is used to detect these faults, a pulse producer and a detector is placed on opposite sides of the detector. The safe detector...
  25. N

    Calculate the Sound intensity level

    Homework Statement A jackhammer with a sound power of 10 W is operating in the countryside. Calculate the intensity levels at distances of 2.0 m and 50.0 m from the jackhammer. Calculate the corresponding levels in dB. Homework Equations β = (10dB) log (I/Io) where, β = sound...
  26. S

    Snell's Law for Light and Sound

    A laser beam and a sound wave from directional sources both enter a liquid at an angle of 60 degrees from the horizontal surface of the liquid. The speed of sound in the liquid is 1.8 times that of the speed of sound in air. For light, the refractive index of the liquid is 1.8. What happens...
  27. G

    Exploring Organ Pipes: Standing Waves and Sound Intensity

    hi could somebody explain to me how organ pipes work? so far, i figured out that there are standing waves in an organ pipe, that are determined by the length and the question of whether there is a closed or open end. but what determines the intensity between these possible frequences(e.g...
  28. M

    How to find energy of sound wave

    Homework Statement In room temperature air, which of the following sound waves would have the greatest energy associated with it? A. A wave with lambda equal to 4.7 on B. A wave with a frequency of 2.6 Hz C. A wave which has a distance between adjacent nodes (1/2lambda) of 21mm...
  29. B

    Is superposition dependant on the measurement of sound as well as sight?

    I understand that an object can exist in many possible locations, and that when you're not looking, it is a wave. It's only when you look that it manifests itself into a particle. But Is that also dependent on the measurement of sound? Does an object materialize when you hear it, or feel a force...
  30. W

    Speed of sound with a ball on the end of a string

    When I was younger I had a ball on a string. For what it's worth, the ball was quite a dense rubber, and about two inches in diameter and spherical, so I think it weighed about two-and-a-bit ounces, maybe two-and-a-half. The string was about a metre long, and it was very stretchy... Once I...
  31. S

    The difference between sound and music

    What is the difference between sound and music? What is the basic property of music?
  32. L

    How does stationary sound waves in open tubes happen?

    This is not a question as such, but it's for answering a homework question. I understand how stationary sound waves in a closed tube are formed, as they reflect off the closed end and the two waves traveling in opposite directions interfere to form a stationary resultant wave (that's how I was...
  33. P

    Amplitude Of Single Tone Sound Wave = Loudness ?

    Amplitude Of Single Tone Sound Wave = "Loudness"? Hello, Given a single tone sound wave: x(t) = A * sin( 2 * pi * freq * t ), what does the 'A' actually represent? Peak Intensity? Intensity Level? Peak Amplitude Pressure? What is adding to my confusion is this link...
  34. M

    What's the relationship between the amplitude and the Sound power level?

    Okay, so I have a sound wave (a visual representation). From this I can see the amplitude of the wave, However, I need to know what the sound power or the sound pressure level. Could someone please give me a formula that could help? Thanks
  35. A

    Sound down a tube (eg shotgun mic)

    I want to be able to figure out how sound works down a tube. Leading to me being able to calculate where I should place slits on a tube and at what size given a tube diameter (and length if necessary) to make a good shotgun mic tube. The slits allow wave cancellation. So there is some...
  36. A

    Locating the source of a sound

    Not sure which section to post this in, but here goes. It's entirely my own words - might look like homework but it's for electronics. Multiple microphones are connected to a computer. A sudden sound, like a gunshot, goes off in the distance. These microphones are separated from each other by a...
  37. O

    How to determine harmony frequency in sound?

    If a sound frequency is given at 1800Hz, how can I determine what range of low frequency would create a harmonic or non-harmonic (which is opposite with harmonic) vibration with 1800Hz? Thanks in advance for any suggestions
  38. J

    Sound intensity level, decibels

    A student typing in a computer cluster generates a sound level of 55 dB. What will the dB level the night before essays are due when there are 30 equally noisy students working in the cluster? dBo = 55 Ihearing = 1E-12 W/m2 Bo = 10log(I/Ihearing) 55 = 10log(I/Ihearing) 55 =...
  39. C

    Exploring the Speed of Sound: Explosive Examples and Visual Demonstrations

    Hello there, I'm making a presentation on the speed of sound in a few days and I was wondering if anyone knows where I can find a video that shows a (preferably huge) explosion from a distance with a timer on it. What I wish to convey from this video is the fact that the light from the...
  40. T

    Change in sound intensity over distance

    Homework Statement You are standing in between two sets of railroad tracks. On one set of tracks a train is initially 200 m away and approaching you with a constant speed of v0 = 11 m/s. On the other set of tracks second train is at the same distance and moving away from you at the same...
  41. O

    Any device to measure sound frequency below 20 Hz?

    Does anyone have any suggestions on what device can measure sound frequency below 20 Hz? Thanks in advance for any suggestions
  42. A

    Why do lower frequencies travel farther than higher frequencies?

    When you try to listen to music through headphones you can reasonably hear the low end (lower frequencies). When you take the headphones off of your head and place them far enough away you only hear a tinny sound. When you are outside of a loud rock concert, maybe 1500ft from the source, you...
  43. D

    Sound wave in a tube of air with holes (lab)

    Homework Statement I had a Physics lab with the following setting: A signal generator is connected to a speaker which is located on one end of a tube. This creates the sound wave. The tube is open on both ends. A micro is movable along the tube and it is connected to an occsilator which...
  44. Z

    Sound Wave Physics: X-Axis vs. Trough

    Hi, easy one but can't really get my head around it. The physics teacher today showed sound as Sine wave on an oscilloscope. If I was actually listening to this sound wave, where would it be silent, on the x-axis or at the trough? Please explain.
  45. P

    Adding more than two coherent sound sources of different phases

    Does anyone know how to add more than two coherent sources that have different phases? An example might be a sound source and a receiver with sound reaching the receiver directly and by two reflections via different paths - maybe off a hard floor and hard ceiling. There's a good document...
  46. L

    Calculating Energy in Sound Wave

    Homework Statement How does the sound energy level produced by woodwind instruments (a piccolo, a clarinet, and a bassoon) compare to the sound energy level produced by string instruments (a violin, a cello, and a double bass) and brass instruments (a trumpet, a trombone, and a tuba)? I am...
  47. O

    Understanding Sound and Bulk Modulus: Formula, Interplay, and Phase Dependence

    I am trying to understand what the formula v=sq rt( Bulk Modulus/density). I understand that Bulk Modulus is indicative of a Pressure force and shows how much an object resists being compressed. So if we take a solid, it will have a greater Bulk Modulus than a liquid and so sound will travel...
  48. J

    Explanation of the sound from the toy puzzle

    My 2 year old play with the following toy at our home. https://www.amazon.com/dp/B000GKD006/?tag=pfamazon01-20 It is basically, when you put the correct animal block in the correct place, it makes the sound of that animal. I can see some sensor in the wood piece and in the board; it can...
  49. P

    Air vs Water Sound Wavelengths: Calculating at 10°C | Grade 11 Help ASAP

    Please solve showing all work asap thanks sooo much How many times more wavelengths occur in air than in water for an air temperature of 10 degrees Celsius if the speed of sound in water id 5220 km/hour and the frequency of sound is 500 Hz. Grade 11, thanks so much please ASAP
  50. A

    Physics based piano sound synthesis

    I'm working on the mathematically modeled piano synthesizer. Right now I'm using modal based approach, where the sound is formed by a sum of exponentially decaying sinusoids (harmonics). Right now I can calculate frequencies of sinusoids (taking inharmonicity into account, of course). For...
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