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. B

    Why Phone Charger Makes High Frequency Sound

    Hi. I noticed that my phone charger (output: 5V DC) makes a constant high pitched noise when plugged into the wall. It's not too loud but you can hear it when you are within maybe 4 ft of the charger. When I plug my phone in, it starts making intermittent noises. I was wondering what this could...
  2. M

    Sound radiation from a pulsating sphere

    Homework Statement Consider a pulsating sphere of radius 0.15m pulsating at a frequency of 2000Hz and surface velocity v_{}0=0.07m/s. What is the distance r, where the measured acoustic pressure is 5x10^{}-2. speed of sound c=343m/s mass density of air ρ_{}0=1.25kg/m3 Homework...
  3. R

    'Doppler Effect' advanced Sound Wave question

    When a car is approaching it has a higher frequency and shorter wavelength. When it has passed sound waves are a lower frequency due to a longer wavelength. Question: Does the higher frequency contain more energy when compared to the low frequency? IF IT DOES NOT, then could it possibly be...
  4. G

    How Does Distance Affect Sound Intensity Levels?

    Homework Statement The sound intensity level of a certain sound source is measured by two listeners located at different positions along a line from the source. The listeners are located on the same side of the source and are separated by 34.8 m. The listener that is closest to the source...
  5. 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...
  6. E

    What is the intensity of sound 2?

    Homework Statement Sound 1 has an intensity of 39.0 W/m^2. Sound 2 has an intensity level that is 2.5 dB greater than the intensity level of sound 1. What is the intensity of sound 2? Homework Equations I=energy/area*time β=(10dB) logI/Io Io=10^-12 W/m^2 The Attempt at a Solution...
  7. S

    What is the delay between seeing lightning and hearing thunder?

    Homework Statement Lighting strikes the ground 1.00 km form an observation point. Calculate the delay between seeing the flash and hearing the thunder. (Temperature @ 15⁰C)(Speed of light = 2.99 x10⁸ m/s) Homework Equations v=331+(0.6)T The Attempt at a Solution Speed of the...
  8. 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...
  9. F

    Exploring the Phenomenon of Sound Waves Near Black Holes: A Fascinating Study

    Hi, I'm doing some research on sound. I'm interested in finding out what happens to a sound wave just BEFORE it reaches a black hole and what happens when it ACTUALLY reaches a black hole ? Can someone direct me to the right place for this ? Thanks for the help
  10. M

    Sound velocity in a moving fluid

    what's difference of sound velocity in a stationary fluid compared to a moving fluid? regards
  11. M

    Understanding Beats: The Interplay of Air Pressure in Sound Waves

    What would happen if an air pressure increase from one sound wave were located at the same place and time as a pressure decrease from another of the same amplitude?
  12. R

    What is the relationship between salinity and the speed of sound in water?

    I've preformed an experiment about the speed of sound waves in water and I found that sound traveled faster in hot water than cold water (distilled water), but it traveled still faster in salt water. So, how can I explain why the speed of sound increases with salinity? We have the equation: c=...
  13. S

    Sci Fi writer with question about sound inside of tunnels.

    I am wondering if sounds would be noticeably different inside of a tunnel made out of ice than for a tunnel made out of dirt/planet's crust. If so, can you think of any comparisons or general differences. For instance, would sounds echo louder/farther in one of them? I suspect the properties...
  14. F

    How Far Must You Be from a Horn to Avoid Pain?

    Pain from Horn Sound. (Solved Already) Homework Statement At a distance of 15 km, a 110 Hz horn, assumed to be a point source, is barely audible. At what distance would it begin to cause pain? Homework Equations 1.)I(4 pi R^2) = I2 (4 pi R2^2) 2.)P= I(4 pi R^2); power at the point source...
  15. K

    Sound frequency dissapate's, By how much?

    Hi there, I am currently got a little project in my head, and though I am good at science i don't know enough physics to work this solution out and i was hoping someone would be able to help. Now i know sound wave diminish over time, but by how much and how fast, here my problem if i...
  16. T

    How Do Distance and Power Affect Sound Intensity Levels?

    Second problem of the day...:blushing: Homework Statement (part 1 of 2) A spherical source radiates sound uniformly in all directions. At a distance of 52 m, the sound intensity level is 46 dB. At what distance from the source is the intensity level 13 dB? Answer in units of m...
  17. 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...
  18. M

    Frequency of sound in a pipe question

    Homework Statement Shown in the picture attachment. The Attempt at a Solution Hello! with this question I am just completely lost. I haven't the slightest clue how to get started. Anybody care to explain why the answer is D? (I've looked at the markscheme..)
  19. R

    MATLAB Solving Speed of Sound in a Liquid - Matlab Experiment

    The following is part of an experiment about the speed of sound in different depths of a liquid, I'm trying to solve it in Matlab. http://img546.imageshack.us/img546/5952/20120408201206.jpg Here is my attempt: clc clf N=13; d=1900:-100:700; t=[2.62 2.37 2.35 2.25 2.09 1.86...
  20. 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...
  21. S

    Help: Sound created over/in subspace? (SciFi)

    Help: Sound created over/in subspace? (SciFi) I know nothing, called basic high school physics and chemistry. However, do not hold back in your answers I do find ways to comprehend what people tell me. This might be a silly question but since audible "sounds" can't travel over empty...
  22. 4

    What is the Frequency of Sound in Air at 11°C with a Wavelength of 4m?

    What frequency of sound traveling in air at 11 oC has a wavelength of 4 m? From what I can come up with... the frequency of sound at 20C is 344 m/s and at -20C is 320 m/s. From this I interpolated and got at 10C it is 332 m/s and then kinda guessing at 11C it is 333.2 m/s. 333.2 / 4 m =...
  23. majormaaz

    Sound Intensity and Bird Watching

    Homework Statement A bird watcher is hoping to add a particular song bird to the list of species she has seen. If a person, only 2.35 m from the bird, hears the sound with an intensity of 1.9 10-6 W/m2, how far could the bird watcher be from the bird and still hear it? Assume no reflections or...
  24. L

    This may sound silly but why did I not get accepted to the REUs I applied for?

    Ok, I applied for 10 chemistry REUs this year. I have only heard back from a couple of them so far, but both were rejections. Now, obviously I still have a lot of opportunity to get a different one, but right I'm just sitting here wondering why I wasn't accepted. Going into senior year 4.0...
  25. M

    Posibility of sound to put off fire.

    Hi all i am now prepar to write a essay about use sound to put off fire, and the pre-reserach i have done have show that the sound do can put off fire, however the very low efficient. What i want to find out how can i extend its distance to put out fire, i have try something ,and some of them...
  26. G

    'speed' of sound vs. 'feel' of sound? (e.g. subwoofer, tree falling, etc.)

    'speed' of sound vs. 'feel' of sound? (e.g. subwoofer, tree falling, etc.) When bass plays from a subwoofer, a tree falls, a bomb explodes or something similar there's a very real physical sensation that accompanies the sound. My mind is most curious to know if these travel at the exact same...
  27. 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...
  28. 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...
  29. Artlav

    Modulating LED light with sound?

    Hello. I'm trying to make an LED light to carry sound, in a simple blink-it-like-it-arrives way. The problem is, on the receiving end the sound arrives with a lot of distortions, most apparent in the lower notes. Single tones are reproduced faithfully, but anything more complex sounds like...
  30. 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...
  31. M

    Using Sound to Read Discs, instead of EMRs.

    Hi all, I was just reading a bit on the disc reading. It was only then that this idea of using sound to read discs struck me. We know that sound too, behaves like light, in many situations(has a particular speed limit, both exhibit resonance, etc.). One very important difference being that...
  32. F

    How Does a Sound Meter Interpret Different Frequency Ranges?

    Hello Forum, I am planning to buy a noise meter. This instrument receives a signal that carries a certain total power. A spectrum analyzer tells us how this total power is distributed among the various frequency components. When the sound meter gives a reading in the dB (A) scale it is...
  33. C

    How Loud is a Rock Band in Terms of Power Output?

    Total Power output Sound! All right, nevermind, problem resumed. . A rock band has an average intensity level of 110 dB at a distance of 15 m from the speakers. Assuming the sound is radiated equally over a hemisphere in front of the band, what is the total power output? Relevant...
  34. P

    How many wavelengths of sound are between the two animals?

    Homework Statement A rhinoceros is calling to her mate using sound wave whose frequency is 5.0 Hz. Her mate is 480 m away. The air is 35°C. How many wavelengths of the sound are between the two animals? Homework Equations v = 331 + (.6)*T v = wavelength*frequency The Attempt at a...
  35. R

    Formula for sound dissipation in air?

    Is there an equation that deals with the dissipation of sound waves in air? As in, how much they die out with distance, because we know they must, otherwise you could hear me talking now!
  36. F

    Ship and Iceberg - Speed of sound question

    Homework Statement 17.While cruising the North Atlantic in a fog, a ship blew its horn, and received an echo from an iceberg 4.0 s later. The temperature of the air was 5°C, the temperature of the iceberg was 0°C, and the temperature of the water was 2°C In order to calculate the distance...
  37. R

    Linear Motion: calculating height of cliff given speed of sound and time

    Homework Statement A student standing on top of a cliff drops a rock down below into the water and hears it splash 3 seconds later. The speed of sound is 330m/s, what is the height of the cliff Homework Equations v= d/t v2 = v1 + at d = v2-1/2 at2 d = (v1 + v2)t v2 squared = v1...
  38. B

    Sound speed = ultrasound speed?

    Hi, I'm doing a lab report and I need to know if ultrasound speed in the air is the same of sound speed in the air. Thank you
  39. D

    Can Kinetic Energy in Electromagnetic Waves Explain Their Speed in a Vacuum?

    Does anyone have an explanation for why kinetic energy carried by electromagnetic radiation travels at the speed of light? My understanding of the speed of sound is that the denser the medium, the faster the wave velocity. Since this is just kinetic energy propagating through a medium, how is...
  40. I

    Will sound be affected by gravity in this simple problem?

    Homework Statement Assume the air temperature is 10.8o C, and the speed of sound in air is 337.8 m/s. Suppose the lab floor is 2.61 m beneath the motion detector. If the detector produces a click, how long would it take before the echo returned? Homework Equations s=Vi*t +...
  41. K

    Lighting and Sound Careers and Jobs?

    I have always been interested in light and sound design (mostly at concerts) and was wondering how could i get into a job or something that will help me get involved into that field ? i don't really want to go through my schools theature program just because i don't like it but yeah help me
  42. H

    What happens to wavelength of sound in liquid?

    We know that speed of sound in liquid is more than in air. Also, velocity of sound = wavelength X frequency. Now there's a change in speed of sound from air to liquid, so, wavelength or frequency should have got changed... But, generally, frequency won't change for an object (correct me...
  43. P

    Free Fall(gravity) with speed of sound in air

    A pebble is dropped into a deep well, and 3.0s later the sound of a splash is heard as the pebble reaches the bottom of the well. The speed of sound in air is 340m/s. (A) How long does it take for the pebble to hit the water? (B) How long does it take for the sound to reach the observer? (C)...
  44. J

    Need assistance building sound controlled LEDS

    I am building a moving target system for a shooting range. It will have a 40 foot target moving perpendicular to the shooter. I have not had any problem with fabricating the target system, but I want to go above what the customer requires. Hopefully this lead to more work for myself in the...
  45. K

    What is the Speed of the Car Based on the Doppler Effect of Sound?

    Homework Statement A policeman detects a drop of 10% in the pitch of the horn of a motor car as it crosses him. If the velocity of sound is 330ms^-1, calculate the speed of the car. Homework Equations f2 = f1 [v - v(listener)]/[v - v(source)] where f2 = apparent frequency f1 =...
  46. B

    Discover the Science Behind Physically Inverting Sound Waves

    First off, I'm new here so I'll do a brief introduction: I've never taken a physics class, but am taking AP Physics next year (didn't know they offered it at my high school). I'm also a musician and wannabe engineer, so I'm really interested in sound properties, acoustics, etc. So that's me...
  47. H

    Can conversion of medium occur in sound?

    If vibrating object produces sound in air and there's a solid object in front of it after some distance, will those sound waves(which were propagating in air before) start propagating within that same solid object or reflected or absorbed or etc. Please explain also. Thanks.
  48. S

    Does this potential fall semester schedule sound too intense?

    This is my first post on here, so I apologize in advance if I'm in the wrong section or something. I was thinking about having this as my schedule for the fall semester. -Analysis I -Discrete Mathematics -General Physics I -Data Structures I'm not sure if I'm being overly ambitious...
  49. M

    Help with a physics sound problem.

    1. Two identical strings on different cellos are tuned to the 440-Hz A note. The peg holding one of the strings slips, so its tension is decreased by 1.5%. What is the beat frequency heard when the strings are played together? f₁=440Hz; Tension decrease=1.5%2. f(beat)=|f₁-f₂|3. f₂=440Hz -...
  50. F

    Sound and air movement: do they affect each other?

    Hello Forum. I have two basic sound questions: I know sound (large wavelength) diffracts a lot when it exits an aperture. But if someone is speaking and he/she is not facing us we still hear them, even if we are in an empty field. Does sound diffract so much that it ends up even behind...
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