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. F

    Rocket travels into space, emits sound - intensity/time question

    Rocket travels into space, emits sound -- intensity/time question Homework Statement A rocket, starting from rest, travels straight up with an acceleration of 56.7 m/s2. When the rocket is at a height of 722 m, it produces a sound that eventually reaches a ground-based monitoring station...
  2. M

    MHB Archer and Sound Travelling Problem

    An archer fires an arrow, which produces a muffled "thwok" sound after it hits a target. If the archer hears the "thwok" exactly 3.0 s after firing the arrow and the average speed of the arrow was 33 m/s, what was the distance sepa*rating the archer and the target? Use 340 m/ s for the speed of...
  3. V

    Longitudinal Waves in Air (Experimentally determining the speed of sound)

    Problem: In my physics class, we conducted an experiment involving a column of air set vibrating by a tuning fork of a known frequency f held at the upper end. The wave travels from the source to a fixed end (namely the water in the lower end of the tube) & reflected back to the source...
  4. S

    F = MA 2011 # 14 (Creating a uniform sound)

    Homework Statement See: https://aapt.org/physicsteam/2012/upload/exam1-2011-1-3-answers_1.pdf Number 14 Homework Equations None that come to mind The Attempt at a Solution I think this is a conceptual question where each needs to be more proportionally spread apart because it...
  5. B

    The physics behind human whistling-where does the sound come from?

    The physics behind human whistling--where does the sound come from? In most whistles, air is split somehow. When humans whistle (by forming a small hole with their lips), this is definitely not the case. I would assume that the mouth is the resonance chamber because pitch can be altered by...
  6. J

    Can sound waves travel in a material at a speed faster than the speed of sound?

    I'm just trying to get a better grasp on sound waves and shock waves. Let's say I have a cylindrical rod of length L with no forces acting on it, and I push on the back of it with some constant velocity less than the speed of sound, c, of the material the rod is made of. Will the front of the...
  7. A

    What is the Optimal Sound Frequency for Echoes Using a Single Slit?

    Homework Statement Hey guys, I'm having a hard time understanding this whole waves chapter and my teacher just gave us a tricky problem... So you have a single slit and it accommodates 3-6 wave lengths across its diameter. Assume that the sound created when echoing off objects may be...
  8. G

    Sound Intensity and Threshold of hearing

    My textbook says that in the equation β= 10log(I1/I2), I1 in most cases is the threshold of hearing (1.0x10^-12). Just out of curiosity, when is I1 not the threshold of hearing?
  9. O

    Sound in Bose Einstein Condensates.

    Hello there I love physics, so I normally read a lot of physics books. I am fascinated about BECs and their possible applications. I've read about BECs and BEC vacuum theory, also that is possible to create black holes in superfluids (as BEC) using sound (sonic black holes). As far as I know...
  10. N

    Finding velocity of a vehicle using Doppler Shift for sound

    Homework Statement You are standing on the side of the Trans-Canada Highway as the Physicsmobile approaches you. As it approaches, you hear an engine noise of 1100 Hz. After it passes, you hear an engine noise of 950 Hz. How fast was the Physicsmobile travelling? Homework Equations...
  11. N

    Sound generated when a cup of water is hit

    Hello I have some questions regarding the following problem: Imagine I have a glass beaker partially filled with water. Assume that I were to hit the beaker (say at the top edge to be specific) with a noodle stick. Assume that I do not hit again until the vibrations have completely died...
  12. B

    Sound intensity and relationship to pressure and displacement

    Homework Statement The sound from a trumpet radiates uniformly in all directions in air with a temperature of 20 degC. At a distance of 4.80m from the trumpet, the sound intensity level is 47.0dB. The frequency is 576Hz. Also knowing speed of sound in air is 344m/s, the density is 1.20kg/m^3...
  13. D

    Does the single diffraction work for sound wave

    PIC (A) http://imageshack.us/a/img37/941/img20130104192537.th.jpg PIC (B) http://imageshack.us/a/img23/5496/img20130104192554.th.jpg I hope you can ans it in a simple way as I am just a secondary 6 student :) thx! For pic a, 1. I dun understand why interference occurs when there is 1 slit...
  14. S

    Does dark matter act as a medium for sound to go through?

    The title basically says it all, I'm wondering whether dark matter will allow sound to pass through because if it does, that could lead to being a way how to detect dark matter.
  15. T

    Experimentobtaining sound from molecules

    Was just wondering whether or not it was at all possible to create "sound" from molecule interactions, and if so how would I go about it? I was going on the theory that if E=hv then a frequency is obtained when this equation is applied and as sound is theoretically a frequency (movement of...
  16. S

    Cross Correlation of two sound signals

    Hello! We are trying to verify if an acoustic standing wave has been established in a cavity. In order to do so, we are giving a constant frequency signal to a speaker. We are picking up the signal at two locations, one very close to the speaker(reference signal) and at a particular...
  17. J

    Calculating distance using the speed of sound through two different mediums

    Homework Statement David is swimming when he hears a beaver sap the water with its tail, first through the water (v= 1400 meters/second) and then 0.95 seconds later (after the sound reaches him through the water) through the air (v= 340 meters/second). Homework Equations Find the...
  18. L

    Sound interference and whistle

    Homework Statement A car honks a 2kHz tone and is 40m from a long high wall. A man is running parallel to the wall, 10m away from it, at 5 m/s, and is presently 30m away from where the whistle is closest to the wall. How many beats/second will be heard by the runner as he will hear the direct...
  19. A

    Sound waves in even dimensions

    I read on the 'Ask A Mathematician/Ask A Physicist' blog that sound waves behave differently in an even-number of dimensions than they do in odd-number dimensions - that they 'double-back'. Why is this - and what does 'double-back' mean...
  20. N

    Types of Piezoelectric Crystals to Harvest Sound

    I am in the process of building a piezoelectric device to harvest sound with a frequency generator at one side of a plastic/glass tube which sends out a low frequency which is then picked up by a piezo disk which send the energy to an led which demonstrates hoe sound can be converted to...
  21. O

    MCQ about intensity of sound waves (formula manipulation)

    Homework Statement Homework Equations The equation that is already given + (maybe) I is proportional to A2f2. The Attempt at a Solution I took the square root of 8, 8 being the Amplitude and I being proportional to the square of A. (I make the constant of proportionality 1)...
  22. W

    Quick speed of sound question?

    A swimmer sees a parachutist hit the water and hears the impact twice, once through the water and the second time through the air, 1.0 s later. How far from the swimmer did the impact occur? Vs air = 340 m/s Vs water = 1400 m/s the answer is 450m I don't understand what to do...
  23. F

    Sound waves question - vibrations and amplitudes

    A tuning fork vibrates 235 times in 3.1 seconds with an amplitude of 0.59mm. Determine.. i) its frequency ii) its period iii) the distance the end of one of the fork tines travels in one second for i) The answer I got is f=75.81Hz ii) The answer I got is 0.13s iii) ?
  24. ghalimoglu

    How can i block the sound outdoor ?

    first of all sorry for my bad english. i know i need to improve it :) now, let's talk aobout my question. You know there is a few ways to block sound indoor with sponge or some materials. i searched on internet but i coulndt find anything to block sound outdoor. i have a project and i need...
  25. K

    Determining the speed of sound from a half-open open pipe

    Homework Statement An observer listens to a vibrating string using a cardboard tube of length 1.4m placed close to his ear (one end closed). The string is excited so as to vibrate at its fundamental frequency, and the tension is increased slowly. The intensity of the sound heard by the...
  26. K

    Modelling sound waves in gases with Kinetic Theory

    I am trying to find a description of sound waves and speed of sound in gases using Kinetic Theory. I mean to derive the sound waves in a medium like gas , composed of molecules moving and colliding as Kinetic Theory describes. The origin of the sound wave, as our experience shows, is the...
  27. E

    Sound Diffraction Explained: What Is It & How Does It Work?

    Hi, my friends. Today, I come up with a question suddenly. It is about Sound diffraction. why can we hear someone's voice even when he is in a closed office. Many books says that it is because of Sound diffraction. But I can't understand. how does it happen? would you be so kind to explain it...
  28. P

    For what slide extensions will trombone produce max sound intensity?

    Homework Statement A 285Hz sound wave is directed into one end of a trombone slide A microphone is placed at the other end to record the intensity of sound waves that are transmitted through the tube. The straight sides of the slide are 80cm in length and 10cm apart with a semicircular bend...
  29. W

    Finding the strongest beat in a sound wave using autocorrelation

    Hi everyone, I have a sound wave representing a piano piece played at a steady tempo, and would like to get a graph of the saliency of each beat (essentially, a probability distribution for how strong each possible tempo is). I understand that this is done by plotting the autocorrelation...
  30. A

    Could a man hold sustained flight using sound?

    I was reading an article on Acoustic Levitation http://science.howstuffworks.com/acoustic-levitation2.htm and near the end it said This got me thinking about the character Banshee from X-Men Who's power, as described by the X-Men wikia is Now I understand that this is not the same thing as...
  31. J

    What is the best air density for sound quality.

    Because obviously too much density gives terrible sound quality, like in water. So is the answer simply the density of our lower atmosphere because that is where our ears evolved? Or has this been tested and found to be a specific density?
  32. S

    The diffrence between refraction of sound and light

    I was thinking about refraction of waves and I´m a little unsure. I wanted to run my understanding through you guys to make sure I´m right. So The general rule is when a wave goes from a slower medium to a faster medium the wave should turn sligtly away from the faster medium when it...
  33. Julio Cesar

    Calculate the height from the speed of sound

    Homework Statement You drop a stone down a well. You hear the 'splash' 1.63s later. How deep is the well? The speed of sound in air is 343m/s. Homework Equations Kinematic equation: Δh=V0t+1/2gt2 Also, I've narrowed the problem down to the total time of 1.63s is equal to... 1) the...
  34. K

    Is it possible to split water with sound wave?

    I have been researching about splitting water including electrolysis, but I came across about using ultrasonic sound wave to split water, I search around and it said that water will decompose at 42000 hertz, is this true, because I am going to do it for my project. May anyone please give me a...
  35. J

    Sound attenuation barrier height (trigonometry)

    Homework Statement http://img543.imageshack.us/img543/4598/photosfr.jpg Find dss, dsr and thus hs. Homework Equations trig The Attempt at a Solution dss = hs/(sin[θ]) dsr = hs/(sin[∅]) dss = 3.059/(cos[θ]) dsr = 47.191/(cos[∅]) θ = arctan(hs/3.059) ∅ = arctan(hs/47.191) I have tried...
  36. A

    Difference between blast, shock, pressure and sound waves?

    What are the differences (I'm really trying to understand the differences in the context of an explosion). When you hear it, are you hearing all 4 waves? Which waves cause the damage and why - why not the others? Also, when NASA launches the space shuttle, they release water to absorb the...
  37. S

    Finding the vibrations of a Membrane, given some sound

    Hey everybody, I'm trying to figure out what the vibration modes of a circular membrane would look like if we put some sound through it. As you may know does a circular membrane with clamped edges at radius a behave according to the wave equation. The general solution thereof has the form...
  38. A

    Question on the relationship between intensity of sound, amplitude and 1/r^2

    Homework Statement Suppose sound wave is emitted uniformly in all directions by a speaker. At a distance of 1.1m, the amplitude of it sound is 1.2x10^-8m What is the amplitude of sound at a distance of 1.7m?The Attempt at a Solution What I'm confused is why does the amplitude of sound change...
  39. H

    Felix Baumgartner and the speed of sound

    Doesn't Felix have an advantage when breaking the sound barrier since the air in which he is moving is less dense, therefore the speed of sound itself is considerably slower? (Felix Baumgartner is the man who recently jumped from 128,000 feet in an attempt to become the first man to break the...
  40. B

    Why Doesn't Hand Swaying Produce Sound?

    Why doesen't hand swaying produce sound and why does my slight scratching my skin produce an audible sound?
  41. S

    Sound Intensity Level of Three Objects

    Homework Statement Given that: TI1 + TI2 = 70 dB TI2 + TI3 = 80 dB Find TI1 + TI2 + TI3Homework Equations TI = 10 log (I/Io)The Attempt at a Solution From that two equations, I got: I1.I2 = 10-17 I2.I3 = 10-16 I1.I22.I3 = 10-33 Then stuck...
  42. R

    What Could Be Causing a Buzzing Sound From My Camping Stove?

    hello physicsforum. i came here hopefully someone can answer this. heres what happend: i was out suing my camping stove. after i turn it off, and start packing it away, i shone the flashlight onto it and that's when i first discovered that there is a buzzing sound coming from it...
  43. S

    How Loud Is a Firework Explosion at 4300 Meters Distance?

    Homework Statement A firework charge is detonated many metres above the ground. At a distance d1=550 m from the explosion, the acoustic pressure reaches a maximum of ΔPmax = 10 Pa. Assume the speed is constant at 343 m/s throughout the atmosphere over the region considered and the ground...
  44. elementHTTP

    Two atoms and speed of sound ?

    How fast is speed of signal between 2 atoms ? Is it speed of light in electric field and then it slows down to speed of sound at more massive nucleus (p=mv) ?
  45. T

    Sound Channeling Material? Polymer or Other?

    Hey Guys, Been a while since my last visit, as I've been away for a well earnt break.. But recently I've been set a challenge and its baffling me some what, and i wonder if anyone can help pleaseeee:biggrin: Basically long and short of it, a Car Manufacturer has been struggling in...
  46. C

    Finding plane distance from ground, with only a sound recorder and a stopwatch

    Hey! :smile: Was discussing with my friends back then about the interesting usage of physics in daily life when we suddenly had some interesting ideas that would be exciting to experiment on. One of the ideas we had was to calculate the distance and velocity of a flying airplane without...
  47. X

    Frequency of the sound of scratching Nails on Chalkboard

    In order to get my question , first read this please, So it means that when the sound is produced from nails on the chalkboard, the frequency range of this sound is between 2,000HZ to 4,000HZ with the amplitude of the sound is mostly a noise ? and human ears are designed to amplify this range...
  48. R

    Travel Sound Wave: Determine Wavelength, Frequency, etc.

    Homework Statement A traveling sound wave is represented by D(x,t)=0.48sin(5.6x+84t) with D in meter and t in seconds. Determine wavelength, frequency, amplitude, velocity (including direction) and the maximum speed of the vibrating air. Homework Equations Okay, I'm quite confused about...
  49. P

    Answer Checking (Speed of Sound formula, dimensional analysis)

    Homework Statement One formula for measuring the speed of sound in air is: v=\sqrt\frac{kTg}{m} v=velocity T=temperature g=dimensionless constant m=average mass of an air molecule If all units are SI, what are the units of k? The Attempt at a Solution I've done a lot of...
  50. L

    What affects the speed of sound - does viscosity?

    What factors affect the speed of sound besides the temperature? Does viscosity affect the speed of sound? Thanks
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