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. T

    Power from Sound: Fans Create 12.56 Watts 1km Away

    Homework Statement Fans at a stadium produce sound that is heard 1km away, the intensity level is 60 dB. How much acoustic power is generated by the fans? Homework Equations B = 10 log (I÷I_0) P=I*A The Attempt at a Solution I= 10^-12*6^10= 10^-6W/m^2 P= 10^-6*4pi*1000^2 =12.56W However...
  2. M

    Are there exceptions to the rule of speed and energy for waves?

    Today I was presented with dispersion in my introductory physics class. Before this topic was presented we were told of two important rules for waves: 1) The speed of a wave is dependent on the medium in which it travels and 2) the frequency of wave does not change when going from one medium to...
  3. B

    Calculating Distance to a Wall Using Speed of Sound

    Homework Statement The human beings are standing at equal distances from a big and high wall. Distance between them is 150 m. When one fires the gun the other hears two shots in an interval of 2 seconds, using the speed of sound to be 340.298 m/s calculate their distance to the wall. Homework...
  4. J

    Question regarding sound and Earth's rotation

    Hi guys, I am new to the forum and I have what is probably a simple question for most of you. Unfortunately a great deal of people I know have suddenly taken up the idea of a "Flat Earth", and they consistently post things that try to contest that a flat Earth is a far more logical idea than a...
  5. S

    What is the speed of sound in oxygen? 21.50mastering physics

    Homework Statement ___ In 1866, the German scientist Adolph Kundt developed a technique for accurately measuring the speed of sound in various gases. A long glass tube, known today as a Kundt's tube, has a vibrating piston at one end and is closed at the other. Very finely ground particles of...
  6. R

    Can a sound wave be both standing and traveling?

    Apologies if this is a stupid question, I have a reference that says: "An ultrasonic field will be a combination of standing and traveling waves. An increase in the traveling wave will decrease the proportion of a standing wave and vica versa". I'm trying to visualise this, I understand the...
  7. R

    Relating Power output of a sound wave to the pressure....

    ... it's amplitude exerts. During cavitation a sound wave is applied to a liquid and breaks it apart and gas pockets are formed. The frequency and the amplitude of the sound wave effect the bubble/s. My question is, if I have the power output of the device then how would this relate to the...
  8. R

    Some questions about Fourier transformation

    Hi, I'm writting a program in the computer and I've to perform a fast Fourier transform to get the frequency domain information. I've read different website, I've watched some videos, etc and I don't fully understand the whole theory about FFT. I've to say that I don't have a solid mathematics...
  9. M

    How can I wire together two sets of computer sound systems?

    I want to purchase the Logitech z623 and add to it two creative inspire M2600 speakers (only the speakers, not the sub-woofer). The reason for doing this is because the Logitech system sounds really nice, it has an amazing bass, but mids and highs are not the best and I wish they was as clear as...
  10. C

    Speed of Sound and its relation to weight?

    Good day (or night). I am new here, so I hope my question doesn't bother many. If (forgetting other laws of nature) a shoebox where to hit the sound barrier and an F-35 were to do the same. Would the sound waves be equal. Would it sound the same to a ground observer? I always assume that mass...
  11. J

    Music My Daughter's Mystery: Watching 'The Sound of Music

    I was watching 'The sound of Music' for the nth time with my 11 year old daughter. There is a scene at the beginning, the Reverend mother tells Maria to go to the Captain's house. My daughter insists the reverend mother says "the captain's wife died seven years ago". And when the kids's names...
  12. A

    Hearing a Sound Wave: Does Intensity Matter?

    Does the ability of an observer to hear a sound wave depends solely upon the intensity of the sound wave?
  13. kelvin490

    How can shock waves travel faster than sound?

    Shock wave is caused by the disturbance of air by the airplane. When it propagate the mechanism should be the same as that of longitudinal sound wave. Why sometimes it can travel faster than sound? (also see: http://physics.info/shock/ )
  14. Cake

    Is my impression of undergraduate research sound?

    So I'm sitting on a happy GPA and an acceptance letter to transfer to a nice school for the rest of my undergrad, my dreams of a PhD looking bright, and this terror just grips me like a swimsuit out of water. I've never actually talked to a professor about how research works. I've read a lot...
  15. G

    Hear the Sun: Exploring Sound in the Solar System

    I know this is speculation but, if the inner solar system was permeated by a gas which could transmit sound waves (say for simplicity, similar to air), would we hear the Sun burning? And which kind of sound would it be? Which timbre and range of frequencies? Would it be unbearably loud? Or very...
  16. J

    What is the connection between sound and shockwaves in outer space?

    As far as I know sound is vibrating matter. Does that mean it could not exist in a vacuum? In outer space there is much less matter for sound to interact with so my question is, how does a sound generated in high matter places change as it travels to low matter places? For example, if you...
  17. S

    Like spacetime -- can sound be taken as a fifth dimension?

    Like spacetime , can sound be taken as a fifth dimension?
  18. PavanKumar

    Speed of Sound: Constant Irrespective of Source Speed

    Hi, As far as I know the speed of sound is also constant irrespective of the speed of the source. I guess, this is an obvious result of the property of waves. So, why is the constancy of speed of a light wave more important? Please point out if there are any mistakes in my assumptions.
  19. S

    After supernova explosion sound is created....

    After supernova explosion sound is created... so what happens to that sound??
  20. E

    Odd (pretty) waveform for third harmonic of violin E-string

    I lightly placed my finger a quarter of the length down the E-string of a violin and drew the bow, forcing the third harmonic. I used an oscilloscope app to look at the waveform. I got this unusually regular pure pattern...
  21. K

    Sound waves and frequency problem

    Homework Statement A public-address system is usually used in the school assembly to obtain better attention from students. Carry out a study on the factors affecting the audibility of sound. Homework EquationsThe Attempt at a Solution Objective: To study how does the frequency of the sound...
  22. Stephanus

    Speed of Sound in Different Mediums

    Dear PF Forum, Sorry I ask this. I should have googled it or doing the experiment myself. :smile: If a cars runs 50 m/s and at that time fires a missile, the speed of the missile is 100 m/s so the total speed of the missile is 150m/s, is this right? And if we sit at the back seat of an airplane...
  23. N

    What is the power of a sound source placed on a tall radio tower?

    Homework Statement A sound source is placed at the top of a tall (h = 189.6m) radio tower. The source has a frequency of 740 Hz and an amplitude of 19.4 nm at point A. The air surrounding the tower has a density of 1.29 kgm-3 and sound travels through it with a velocity of 343 ms-1. Point A is...
  24. Fluxxx

    Sound as compression or rarefaction of air

    When a loudspeaker moves back and forth, sound is generated. The moving of the loudspeaker diaphragm causes condensation of air when it moves outward, and rarefaction of air when it moves inward. When this movement is happening at a certain frequency, we hear a sound. See for example this...
  25. Mnemonic

    Power of Sound Wave at distance

    Homework Statement A sound source is placed at the top of a (h = 121.5m) radio tower. The source has a frequency of 653.8 Hz and an amplitude of 11.4 nm at point A. The air surrounding the tower has a density of 1.32 kgm-3 and sound travels through it with a velocity of 340 ms-1. Point A is...
  26. kkpanu9

    Help explain Physics Phenomenon

    http://www.quora.com/How-can-sound-waves-alter-the-flow-of-water Ok, so I carried out this experiment, and I understand some of it, but need help with other parts. Ok, so are we actually seeing a sine wave formed by the water? If so, I understand that waves are supposed to transport energy...
  27. M

    Speed of sound and light through different solutions

    If you have the same liquid, water, but with different ions dissociated in it, changing it's colligative properties, does the index of refraction change? And/or does the speed of sound through it change?
  28. A

    Does my accent sound odd? (Video included)

    School's done, and I'm in the middle of summer break, so I've got time to worry about things like this. (Y) I moved to a town 30 minutes from Toronto when I was 2, and have lived here ever since. I was born in Korea, but I thought that I sounded like any other Torontonian. Nope, there's...
  29. S

    How far did the parachutist fall before hitting the water?

    Problem: A swimmer sees a parachutist hit the water and hears the impact twice, once through the water and the second time through the air, 1.0s later. How far from the swimmer did the impact occur. Vs of air is 340m/s. Vs of water is 1400m/s and the answer in the book is 450m. 2. I know this is...
  30. S

    How Can the Speed of Sound Help Determine Room Temperature?

    Homework Statement Calculate the room temperature by using the speed of sound formula and using the given values. Known Data: Frequency = 480 Hz 2nd Resonant length = 54cm or 0.54m Homework Equations v = 331 + (0.60)T T = (v - 331)/0.60 v = fλ (Open-Closed air column) L = (3/4)λ The...
  31. R

    What happens if the new ARX bullet breaks the sound barrier?

    The venturi effect of the new ARX bullet almost doubles side exit velocity. What happens if the exit velocity exceeds the sound barrier in a fluid like a gelatin block?
  32. B

    Difference between sound echo and mirror reflection

    Homework Statement Why is is that when we look in a mirror we expect to see a reflection equally as bright as the real image, but when we stand in front of a cliff and clap our hands we don't hear an echo as loud as the original sound? Homework Equations R = (z2 - z1)/(z2 + z1) The Attempt at...
  33. Kyuutoryuu

    Is there a medium in which sound travels faster than light?

    So we all know that the speed of sound increases with greater density of medium. Conversely, the speed of light decreases with greater density of medium. Does there exist such a medium that is so dense that the speed of sound overtakes the speed of light?
  34. E

    Medical Why do we enjoy listening to music?

    I've been researching this subject for a little while. I'd like to hear your ideas, because the topic is widely discussed. So here is some part of my research which makes my opinion quite clear: "Sometimes we say , that one is moved by music. Of course, it does not mean for him/her to be...
  35. W

    Sound Interference on a speaker

    I had a physics course a few years back that touched on constructive and destructive waves and only today did i notice this phenomenon with my speakers. I was curious about the theory behind this particular scenario in my room. I have one of those mobile speakers, a bose soundlink II. It has 4...
  36. E

    Sound Intensity on a Field (no interference)

    Homework Statement Two loudspeakers on elevated platforms are at opposite ends of a field. Each broadcasts equally in all directions. At the halfway point, the intensity is 74.1dB. What is the sound intensity level at a point one-quarter of the way from one speaker to the other along the line...
  37. D

    How to Optimize Sound Reflection with Multiple Types of Reflectors?

    I have 2 types of sound reflectors on the image attached. The angles are not proportional but you should get the idea. The black circle is the source, the black lines are the waves and the red lines are the reflections of the waves emitted by the source. My target is to reflect the sound waves...
  38. M

    Measuring distance a sound wave travels

    I would like to be able to measure the distance a sound wave travels. This is for a violin bridge and what I would like to do is apply a frequency corresponding to the frequency the string (196 hz for the g string) and determine the distance the wave traveled to get to the foot of the bridge...
  39. S

    "Diffraction: Why Bass Music is Easier to Hear

    Homework Statement If you hear music in the distance, would you be more likely to hear the treble or the bass notes of the music? Using your knowledge of diffraction, explain your answer. 2. The attempt at a solution So I found that the bass's waves are carried at a longer distance than the...
  40. G

    How would music sound in a different atmosphere?

    I guess that the way we experience sounds on Earth is very importantly influenced by the composition and density of our atmosphere, since it determines how a pressure wave will be formed and will propagate. Does music sound appreciably different when heard at very high altitudes with low air...
  41. M

    Absorptive type sound insulation

    Could you tell me the physical reason, why the absorptive type sound insulation (Windowpane with some thickness) is effective only at high frequencies of sound source?
  42. Y

    Total sound intensity from sources

    Homework Statement A family ice show is held at an enclosed arena. The skaters perform to music with level 80.0 dB. This is too loud for your baby, who yells at 75.0 dB. (a) What total sound intensity engulfs you? Homework Equations I ∝ A2 The Attempt at a Solution Why did the answer sum...
  43. Z

    Destructive interference Sound question

    Homework Statement A student enters Best Buy prepared to buy a pair of speakers. Before he does so, he conducts an experiment with them. He places the speakers 4.0 m apart and connects a signal generator to both speakers that produces a single and consistent tone. (constant wavelength and...
  44. D

    Speed of light vs speed of sound

    Hi all,I originally posted this question as a reply to another post, but afterwards I thought it would be better to start a new thread. Unfortunately, I couldn't figure out how to delete the old post. With that out of the way... In the experiment, we send either light or sound from a source...
  45. L

    Which properties of waves are influenced by the medium?

    Which of the following of a wave can be affected by the medium it travels through? (i) wave crest velocity, (ii) wave frequency, (iii) wavelength
  46. D

    The Mystery Behind Atoms Vibrating & Sound Creation

    Hi Likely a stupid question. If atoms vibrate with heat, why don't hot objects make a sound, i.e transferring vibrations to the surround atoms (air) into our eardrums? They vibrate on ultra-infra sound? Or it's a extremely weak sound? or this is not the same vibration as the cause for sound? or...
  47. P

    Doppler Effect and the speed of sound

    Homework Statement You are moving at a speed of 35m/s and hear a siren coming from behind you and observe the frequency to be 1370 Hz. The siren goes past you and the new frequency heard is 1330 Hz. What is the speed of the siren traveling at? The speed of sound in air is 340m/s. f1=1370 Hz f2=...
  48. O

    What happens to the sound wave?

    Ok so it happened again... my students asked a question I hand't thought of before (love it when that happens!) Can you help me? What happens to the sound wave after it hits the eardrum? Does it get absorbed, or does it continue to go through your head? I found lots of info about how the...
  49. L

    How do environmental conditions affect the way we hear traffic noise?

    I'm curious as to why I can hear traffic noise sometimes and not others. The busy hwy is about a mile away across a field. Sometimes it sounds like it is at my door but other times I can't hear it but still see a lot of traffic. How does environmental conditions (temp, no wind, etc) affect the...
  50. Rumo

    Speed of sound in an isentropic ideal gas

    Homework Statement \rho_0, c_0 is the mean density, the mean speed of sound in the ideal gas. Is the following correct? c(\rho)=c_0\left(\frac{\rho}{\rho_0}\right)^{\frac{\kappa-1}{2}} Homework Equations p = const * \rho^\kappa, c=\sqrt{\frac{\partial p}{\partial \rho}} The Attempt at...
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