Sound waves Definition and 333 Threads

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. J

    Interference of Sound Waves in a Circular Tube

    1. A sound wave with frequency f = 2300Hz is sent into a circular tube of radius R=160cm through an opening at some point A. A receiver lies at point B, separated from A by an angle α=130°. The speed of sound in air is v=330 m/s. Sound propagates from A to B in both directions along the...
  2. A

    Light and Sound Waves: Theoretical Analogies and Differences

    Anybody has reference paper on light and sound wave's theoretical analogies? I want to read about the analogies and difference between this interactions in terms of waves. Thank you in advance. AGZ
  3. A

    Focusing Sound Waves: Acoustic Lens & Loss of Energy

    Is there any way to focus a sound wave BEHIND an acoustic lens i.e. the source and receiver are on different sides of the lens? Will it result in a significant loss of sound energy?
  4. Manraj singh

    Speed of sound waves in various media.

    My tenth grade physics textbook says that sound travels faster in solids than air. But it also says sound will travel faster in air if its density decreases. I didn't really get the logic, as solids are denser than air, and that is why sound travels faster. Then they say as temperature of air...
  5. A

    Focus Sound Waves: Can We Refract Like Light?

    Can we focus parallel sound waves using convex and concave lenses since they essentially follow the same laws of refraction as light? If not, is there any way to focus parallel beams of sound to converge at a point?
  6. T

    Question for dangerous sound waves for health effect?

    Which one has the more dangerous health effect...ultrasound or infrasound.? and why...
  7. T

    Question for sound waves effect. .?

    Which one has more dangerous effect for health ...ultrasound or infrasound.? and why...
  8. patrickmoloney

    What Distance from Speaker A Will a Microphone Detect Minimum Sound Intensity?

    Homework Statement Two loudspeakers A and B of equal power are separated by a distance of 1.4 m. Both the speakers emit sound waves in phase and of frequency 450 Hz. If a microphone were to be moved from A in a direction perpendicular to AB, at what distances from A will it detect a minimum...
  9. M

    What is the largest wavelength for maximum sound intensity?

    Homework Statement Two sources, A and B, emit a sound of a certain wavelength. The sound emitted from both sources is detected at a point away from the sources. The sound from souce A is a distance d from the observation point, whereas the sound from source B has to travel a distance of...
  10. Z

    How are square sound waves possible? How does a speaker sustain peak?

    Hello everyone :smile:, after spending many hours watching youtube videos, reading wikipedia articles and other related material, I came to the conclusion that my best hope at understanding this is to have an explanation personally explained to me, and I trust this is the right place to ask for...
  11. P

    Electrical noise ( I mean sound waves )

    Hello physicsforums. What causes noise in electrical cables and/or transformers and/or electrical stations ? By noise I mean mechanical sound waves like bzzzzzzzz, not signal noise. And what is the proper way to search in google for this, I could not find a wikipedia article on this.
  12. adjacent

    Why Do Some Sound Waves Reflect While Others Are Absorbed?

    I think they(longitudinal waves)hits the air,but they are not reflected back because air is very light.In the same way,when they hit a wall,as the wall is not going to vibrate vigorously,Some of the waves are absorbed(i.e. they make the wall vibrate)and the others are reflected back. If I am...
  13. C

    Constructive Interference of Sound Waves

    Suppose two loudspeakers are separated by three meters and are being driven by exactly the same sinusoidal signal at a frequency that can be varied. If you are located four meters away directly in front of one of the speakers, determine three lowest frequencies for which you would hear...
  14. T

    Calculating phase difference of sound waves

    Homework Statement An observer stands 3 m from speaker A and 5 m from speaker B. Both speakers, oscillating in phase, produce waves with a frequency of 250 Hz. The speed of sound in air is 340 m/s. What is the phase difference between the waves from A and B at the observer's location...
  15. G

    Does Constructive Interference Double Sound Intensity at Source Point in Water?

    If two sound sources (A, B) are placed in a water tank and emit sound waves at the same frequency, phase and amplitude, if I measure the sound intensity at point A, will the detected signal will be ~double than the emitted signal of each sound source? I think that the answer is yes because of...
  16. Saitama

    Sound waves - Detector and a moving wall

    Homework Statement A sound source, detector and a movable wall are arranged as shown in the figure. In this arrangement detector is detecting the maximum intensity. If the speed of sound is 330 m/s in air and frequency of source is 600 Hz, then find the distance by which the wall should be...
  17. Saitama

    Sound waves - Destructive Interference

    Homework Statement Two identical loudspeakers are located at points A & B, 2m apart. The loudspeakers are driven by the same amplifier (coherent and are in the same phase). A small detector is moved out from point B along a line perpendicular to the line connecting A & B. Taking speed of sound...
  18. S

    Sound waves: How do we know it is the fundamental harmonic?

    I have done a handful of problems related to sound waves in air columns and one thing I have noticed is that, unless told otherwise in the problem formulation, one always assumes that sound wave that is formed is always the fundamental harmonic and thus the length of the air column comprises a...
  19. C

    Is AC current analogous to sound waves?

    It is really hard to picture current as a wave. The best explanation I have had so far is that the energy is transferred along the wire as a longitudinal wave of compressions of charge density, just like a sound wave is a longitudinal compression of mass density. so consider an open circuit...
  20. Jalo

    Sound waves propagation and the doppler effect

    Homework Statement A lighthouse emits a noise with a frequency of 2000 Hz in the direction of the sea, with a power of 100W. Consider the speed of sound, vs, to be 341 m/s. A ship approaches the coast with a speed of 30 km/h and produces noise with an intensity of 40dB. Consider it is...
  21. C

    Why Do Sound Waves Travel Faster in Steel Than in Air?

    A man hammers on a steel railway track. If you hear the sound through the track 5.0 seconds sooner than through the air, how far away is the man? *Steel - 5960m/s *Air - 346 m/s The question is simple but i can't get it Also please explain how to do a question like this in the answer.
  22. PhizKid

    Sound waves travelling different paths

    Homework Statement Homework Equations The Attempt at a Solution So at the sound source, the waves are split in half I guess, and each of those halves travel into the different directions. Path SAD is constant and SBD is not, so the waves are changing in path SBD. Since the sound...
  23. PhizKid

    How to find distance using sound waves

    Homework Statement Homework Equations x = (v_0)^2 - (1/2)gt^2 The Attempt at a Solution Well, since the stone is dropped from rest, and the down direction is negative, the displacement is: x = -(1/2)gt^2 x = -(1/2)(9.8 m/s^2)(3.00 s)^2 x = -44.1 m. But this is incorrect...
  24. J

    Do sound waves get bigger when they bounce off a wall?

    Homework Statement The questions states, "If you speak while standing in a corner with your face toward the wall, you will sometimes notice that your voice sounds unusually loud. Explain."The Attempt at a Solution Is this because the sound waves are bunched up when they bounce off the corner...
  25. V

    Which Frequencies Will a Listener Not Hear from Two Variable-Frequency Speakers?

    Problem: The problem asks to find which frequencies a listener, whom is receiving sound waves in the same direction from two variable-frequency speakers 50ft and 55ft away, will not hear anything at all. Solution (so far): My approach is to find an expression for the wave coming from each...
  26. 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...
  27. 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...
  28. 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)...
  29. 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) ?
  30. 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...
  31. 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...
  32. L

    Practical question re sound waves

    Hi - I am a lay person with a practical question regarding sound. I live near a busy street and am considering having noise-reducing windows installed. The noise-reducing windows would fit beside (and in addition to) the current window to block out street noise, so in effect there would be two...
  33. D

    Calculating Water Depth Using Sound Waves

    Homework Statement a submarines sends sound waves and receives it after 4 seconds then goes under water 700 m and sends waves and receives it after 3 seconds he wants the depth of water Homework Equations V=d/t The Attempt at a Solution V=d/t V=x/2 then V=X-700/1.5 so x/2 =...
  34. A

    What Would Happen If a High Mass Object Hit a Wall at High Velocity Near Me?

    If an object of VERY high mass were to hit a hypothetical wall at a high velocity and the wall somehow withstood that, what would happen to you if you were standing on the other side close to the wall but not touching it? Would there be some sort of wave transmitted through it? If so, would this...
  35. A

    Fourier Analysis of Real Sound Waves

    If a basic sin sound wave is analysed with a Fourier transform, the result is just a spike at a certain frequency. My maths isn't the best so bare with me... if we take a real sound file and take Fourier transforms at regular intervals (I assume that's what's being done when calculating a...
  36. T

    Sound waves through air column

    hello guys, I'm having problems understanding why if we were to have a tuning fork that vibrates at a particular natural frequency, it will resonate at many different lengths of air column (which means different natural frequency of air column). Does this mean that the natural frequency of the...
  37. S

    What Is the Period of Regular Fading in a Car Between Two Sound Sources?

    Homework Statement A car is driven at 30m/s between two sources, each producing sound waves of 1.50x10^6 Hz. The sound heard by driver rises and fades as he travels from one sound source to the other. Find the period of regular fading. Homework Equations No relevant equations...
  38. A

    Acoustics: Directing Sound Waves

    Hey, I'm just curious if anyone has designed a device that can direct and concentrate sound waves like a parabolic mirror? Since both sound and light are waves, I assume there must be a shape that allows one to "target sound" much like using a magnifying glass to focus light. On a related...
  39. D

    Why Are Sound Waves Invisible to the Human Eye?

    Why can't we see sound waves?
  40. A

    Constructive Interference of Sound waves

    Homework Statement A pair of speakers connected to the same signal generator face each other, one at x=0 and the other at x=1.5m. If they are producing a sound frequency of 2000Hz what are the points (position x) of constructive interference between the speakers? Express your answer in...
  41. C

    Determining Frequency Shift for Moving Sound Sources

    I was considering the following question; 'A fire engine traveling at 70m/s drives past a van traveling at 30m/s. The speed of sound in air is 330m/s and the fire engine has a frequency of 200Hz when stationary. At what frequency does the van driver hear the siren?' I understand you have...
  42. E

    Sound Waves Traveling Down a String

    Homework Statement A brother and sister try to communicate with a string tied between two tin cans. If the string is 9.5m long, has a mass of 55g and is pulled taut with tension 6N, how much time does it take for a wave to travel from one end of the string to the other? Homework Equations...
  43. J

    Sound waves, guitars and polarization

    I'm currently doing some research on sound waves and their relation to making a guitar highly energetic. I have a few questions on this topic that I would like to ask. 1. The waves created on a guitar string. Are they 1 dimensional transverse (standing) waves? 2. Does this vibrational...
  44. M

    Distinction between shockwaves and sound waves

    Hi, I would like to know about what exactly constitutes a shockwave. Let me write out what I understand of it. There are two explanations I have come across. 1) The shockwave is caused when gas particles move faster than the speed of sound due to some external factor (a plane, an explosion or...
  45. P

    Can You Block Sound Waves Entirely?

    Hey guys, I have an average-man knowledge in physics so please simplify your question so anyone could understand :) I had no place for this so I'm writing it here in the general forum.I asked a friend of mine if you can supress sound waves entirely, so you won't hear a thing. to keep things...
  46. C

    Standing sound waves for fundamental and first two overtones

    Homework Statement Standing sound waves are produced in a pipe that is 1.40 m long. For the fundamental frequency and the first two overtones, determine the locations along the pipe (measured from the left end) of the displacement nodes if the pipe is open at both ends. Homework...
  47. Gamma

    Using a microphone to view sound waves on an oscilloscope

    Hello, I want to use and oscilloscope to demonstrate sound waves for our local school science day. I want to be able to allow kids to make different vocal sounds to see how the sound waves look like. I removed the microphone part from a headphone and used it in a circuit to see audio...
  48. E

    Optimizing Resonance Length for Closed-End Pipe with a Tuning Fork

    Homework Statement A tube is closed at one end by a piston which is slowly withdrawn as a tuning fork of frequency 512 Hz is sounded over it. What is the shortest length of pipe which will resonate with the fork? (Speed of sound is 340m/s) Homework Equations L=1/4λ f=v/(4L) The...
  49. L

    In order to achieve beam forming of the sound waves

    hello, i am involved in a private project. for this project it is necessary to control a huge amount of loudspeakers (intensity, frequency) in order to achieve beam forming of the sound waves. However, since i am not an electrical engeneer i really do not have a clue how something like this...
  50. 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...
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