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. M

    What is the equation for decay of natural sound over time?

    Let's say you have an impulse of noise, eg. via a guitar string, or a resonant bandpass filter, and it decays naturally. If "1" is the maximum initial amplitude of sound, and "0" is no sound at all, what is the equation for decay of sound over time (x)? Is it: y = 1/c^x Or y = 1/(x+1)^c I...
  2. D

    Sound of 2 identical horns cancels out?

    I'm wondering if the sound of two identical horns positioned perfectly in front of each other and emitting the same sounds/pressure will cancel each other out no matter what where the only variable changing is how far apart the horns are from each other. Maybe an example would be two clarinets...
  3. K

    MHB Sound measurement percentage in tolerance

    I have a graph measuring 1/3 octave sounds checking if they fall into a range so they are within a defined tolerance. If for example, I have 20 specific 1/3 octave frequencies I am looking at, I can figure out a percentage of which of the 20 frequencies fall in tolerance fairly easily...
  4. mktsgm

    Hear Through Walls: How & Why?

    How and why do we hear through the brick walls? Does the sound actually penetrate the walls?
  5. J

    Maximum gain possible by sound wave focusing

    Just like a concave mirror concentrates light, it can also concentrate sound waves. Ray diagrams like the following look as if all waves converge to a single point of INFINITE power density which of course is not true, probably because of the wave nature of light or sound. What is the correct...
  6. T

    How does the size between scatterers affect reflection?

    If a sound wave hits multiple scatterers spaced closer than the wavelength and moving fast but at different velocities how is the reflective beam is affected?
  7. F

    Sound wave intensity (dB) and sound processing

    Hello Forum, A sound wave intensity (pure frequency) is proportional to the square of the wave pressure amplitude, i.e. ##I \approx p_0^2##, where ##p_0## is the pressure wave amplitude: ##p_0 sin(\omega t \pm kx)##. This means that the (gauge) pressure value goes larger (positive) and lower...
  8. C

    Triangulating Sound: Creating an Extensible Algorithm

    I would like to be able to triangulate a sound's location based on the inputs of two robotic sensors. I know this involves trigonometry, but I am a little out of practice. I think the practice of triangulation also is useful for radio signals. I would like to create a triangulation algorithm...
  9. B

    Kill or incapacitate a pupa with sound?

    Elsewhere there are discussions about the feasibility of killing bugs with ultrasound. All of those discussions consider a situation, presumably, where the bugs are in the air. That seems a tricky problem, but perhaps not the one I wish to discuss. The Problem: So in California we have this...
  10. YMMMA

    Physics: wavelength of sound waves

    Homework Statement Stated in the attached file. Homework Equations Wavelength = 2 times length divided by harmonic I don’t know if it’s the relevant equation The Attempt at a Solution I used the equation I wrote. So, if the left side is 10cm longer, I guess it might be 2(10).
  11. jha192001

    Sound Wave Doppler effect question

    I have seen few examples on Doppler effect and i am confused about one such. We are standing on ground. If the source of sound S moves and Object O is stationary. We would presume the frequency as well as wavelength of sound be changed to the obeject O. But if O moves towards or away from S...
  12. Mahavir

    "A sharp sound is perceived as being more intense than low"

    Hi everyone, Apologies for what may be a relatively obvious question for you but I'm struggling to understand a concept that was discussed in my introductory Physics class. I would really appreciate any help you could offer. During an explanation of sound, we were told today that a sharp sound...
  13. R

    MHB If you are 8 ft away from the source, how long does the sound take to reach you?

    The speed of sound is 761.2 mph, or, according to my math, 1116.5 fps. If you are 8 ft away from the source, how long does the sound take to reach you? What is the formula for doing this? I divided 8 into 1116.5, and got 139.5 - but that doesn't seem to tell me anything. Obviously, the answer...
  14. V

    Does the speed of sound change in metal when heated?

    Is the speed of sound different through the same piece of metal when it is heated compared to when at ambient temperature?
  15. F

    I Variations in the speed of sound in a star

    I try to understand the following graphics with x-axis being the radius of a typical star : I would like to knwo if ##\delta c/c## (y-axis) represents the relative error between theoretical and experimental values or if it represents the fluctuations of speed of sound inside. If these are...
  16. nmsurobert

    Metallica Unveils Blackened Whiskey Enhanced by Sound Waves

    I have some skepticism. All it says is "enhances molecular interaction", which sounds kind of vague to me. They also say it "shapes" the favor. None of which make sense. So either I don't understand how its possible (which is possible) or its some nonsense... which is also possible. Anyways, I...
  17. betamu

    Frequency of Reflected Underwater Sound Wave

    Homework Statement The sound source of a ship’s sonar system operates at a frequency of 18.0 kHz. The speed of sound in water (assumed to be at a uniform 20°C) is 1482 m/s. What is the difference in frequency between the directly radiated waves and the waves reflected from a whale traveling...
  18. Y

    Why do sound waves not bounce off of each other?

    If air is made up real little particles, then why would the waves made up of these particles not bounce off? Here's my attempt at an explanation for the principle of superposition for soundwaves. The wave is transferred by the air molecules hitting the ones adjacent to it. But because air is...
  19. SherLOCKed

    Increase in the frequency of sound in a glass of water?

    Suppose you have a glass of water, and you beat a spoon on the bottom layer of glass through the mouth of glass, repeated beatings in a regular fashion will cause in increased frequency of sound produced due to the spoon beating?What causes such increase in frequency?
  20. P

    What is the Relationship Between Sound and Magnetic Frequencies?

    Greetings! I was asked to provide an introduction: I am a retired Professor, in Music of all fields! I come from a family of engineers. I have long been researching sound and it's relationship with magnetic frequencies. I am also engaged in the development of a battery using permanent magnets.
  21. T

    Speed of sound in steel vs air

    I saw on a web page a video of tiny Agnes Scott College vs Princeton University from 1966 on GE College Bowl.Agnes Scott won (!), but one of the questions that both schools got wrong was asked by the moderator: The speed of sound in air is about 1,100 feet/sec. The speed of sound in steel is...
  22. Quantumfied

    Admissions How does this path sound?

    Hey guys, I’m a junior in Florida studying mechanical engineering. My school currently offers a 4+1 accelerated masters program for mechanical engineering which I’m strongly considering. How feasible is it for me to to do this and then apply for a PhD in electrical engineering to another...
  23. V

    Does the sound or the frequency to repel mosquitoes exist?

    Hi, I have heard much about this, but I'm not an expert. Now I know that mosquito hears by Johnston's organ at antennas. Also that mosquitoes have something like "sound/frequency filter", it means they listen to only some sound/frequency, especially other mosquitoes or other animals. Is it...
  24. prakhargupta3301

    No sound in vacuum? So can I clap more?

    I was just wondering (Wondering!? Stop wasting our precious time!) about clapping my hands. *Claps* It's sound energy. A little energy is released as heat. Good. This means that I have used some energy from my body. In making those two energies. Right. <<Mentor note: rant removed>> So, I am in a...
  25. Dr. Courtney

    Direct Echo-Based Measurement of the Speed of Sound - Comments

    Greg Bernhardt submitted a new PF Insights post Direct Echo-Based Measurement of the Speed of Sound Continue reading the Original PF Insights Post.
  26. S

    What does it sound like inside a pulsar?

    A star is kind of a huge nuclear explosion. Things are smashing into each other all the time, bouncing off, and all this movement creates vibrations, so there's actually sound sound inside any star. Pulsars have produced radio waves, which have been converted into audible sound waves, thus...
  27. V

    Speed of Sound Experiment: Hear the Results

    Imagine a car which has a speaker attached to the back. Speaker is blasting very high volume music towards the reverse direction of the car. Now the car starts accelerating and in a few seconds starts moving faster than the speed of sound. Will a listener be able to hear the sound now. Will...
  28. D

    How does sound intensity affect the current produced by a mic?

    I measure sound (dB) from a speaker at 0cm and 100cm using a diaphragm microphone. 0cm-100dB, 100cm-30dB diaphragm microphone cinsists of a diaphram, coil and a permanent magnet. the coil is attached to the diaphragm, when a sound wave hits the diaphragm it causes to move back and forth which...
  29. E

    Sound Loudness vs Pitch Misconception

    Hello everybody. I am involved in a project aiming to address Physics Misconceptions regarding Sound through the creation of virtual musical instruments. One of the major student misconceptions I have found in bibliography is the fact that students perceive sound pitch and loudness as being the...
  30. Sorcerer

    I Can Light Create Sound in Air? Exploring Momentum Transfer

    If a pulse of light, which has momentum p = E/c, interacts with particles of air, would it not change their momentum over time, causing mechanical energy (sound)? As I understand it, sound is mechanical energy moving through particles as they vibrate. Why can't the momentum of a pulse of light...
  31. P

    A Measuring Viscosity via the Speed of Sound

    Hello, I am on the search for papers, books, etc. on how one can measure the viscosity of viscous materials via the speed of sound. I've searched for a while now and haven't been able to find much on this topic. Any help is greatly appreciated.
  32. M

    Sound intensity of a thunderbolt

    Homework Statement Find the sound intensity of a thunderbolt 1 km away. What sound intensity (dB) is it 1 km away? The thunderbolt can be heard up to 20 km away. The sound is spherical. The air absorbs nothing. Homework Equations L = 10 \cdot lg(\frac{I_1}{I_0}) \Delta L = 10 \cdot...
  33. S

    Can the Speed of Sound Be Measured Using Frequency and Time Delay Data?

    Suppose we have an ultrasonic transmitter and an ultrasonic receiver, separated by some fixed distance ##d##. Both devices are attached to an oscilloscope. The transmitter generates ultrasonic waves at some frequency ##f## that we can change. The receiver is some piezoelectric that translates...
  34. P

    Speed of sound: viscosity dependece in liquids and solids

    Hello, Wikipedia gave me prior hints as to how the speed of sound depends on viscosity but after searching on Google scholar and Google, I have yet to find any direct equations/findings that give a direct relationship of the speed of sound to the visocisty of fluids and solids outside of...
  35. AgustRunarsson

    What is the formula for converting decibels to a power ratio?

    Note: I'm sorry if I have to use the template, but I already have the solution, I just do not understand it and need help understanding it. 1. Question: A firework explodes at a 40 metre height and gives off a bang which measures at 100 dB at ground level. What is the power of the sound that...
  36. S

    Calculating frequency of the second harmonic

    Homework Statement The fundamental frequency of a violin string is 283 Hz. Calculate the frequency of the 2nd harmonic. Known: f = 283 Hz Homework Equations v = fλ f(n) = n*v/2L λ= L v(sound) = 343 m/s The Attempt at a Solution λ = 343/283 = 1.21 m f(2) = 2*343/2*1.21 = 283 Hz. I'm getting...
  37. S

    Question about the physics of sound

    Hello there! I have a couple of questions regarding the physics of sound (they may seem odd and concerning, but aren't for any malicious purposes, I promise, these questions just popped up in my head ) First, I'd like to understand how soundprofing works, the science behind it and how well can...
  38. A

    Calculation for finding distance with regard to sound intensity

    Homework Statement Two amplifiers can be used to power a sound system. Amplifier 1: Has a fixed power output of 300 W. Amplifier 2: Has a variable power output of between 15 W and 175 W. You may assume that the power output of the amplifier is equal to the power of the sound waves that are...
  39. J

    Motion of point when sound volume goes up

    Homework Statement A radio speaker produces sound when a membrane called a diaphragm vibrates, as shown above. A person turns up the volume on the radio. Which of the following aspects of the motion of a point on the diaphragm must increase? a) the max. displacement only b) the average...
  40. R

    Sound Wave Interference: Investigating Null Results with Sound Level Meter Data

    I collected this data by moving a sound level meter slowly through a total length of 0,75 meter between two speakers pointing towards each other. The wavelength of the sine waves was 0,343 meters and the frequency was 1000 Hz. The sound level meter measured the sound in dbA 20 times a second...
  41. aatari

    Sound wave Interference from Two Speakers

    Hi guys I am having trouble determining a quite spot based on where you stand in respect to distance from the speakers. I have solved the question below but I need someone to explain to me how the "n" value can be used to determine a quite or not-quite spot. Am I looking for whole numbers? If n...
  42. M

    What is making this sound? (in a Rotary lobe pump)

    What is the reason making this sound?? ( Rotary lobe pump)
  43. E

    Increase in the volume of a sound

    Homework Statement A person turns up the volume on a radio. Which aspects of the motion of a point on the diaphragm must increase? a. maximum displacement only b. average speed only c. both maximum displacement and average speed d. neither maximum displacement nor average speed Homework...
  44. D

    Instrument to measure the frequency of sound

    I need an instrument to measure the frequency of the sound of a vibrating violin string for a high school research essay. I tried using a Labquest and a vernier microphone to measure but it was way too imprecise. I need the instrument to very accurate in measuring Hz as the nature of my essay...
  45. B

    Measuring the speed of sound in an iron tube

    For physical experiment I have a project in which I have to measure the speed of sound in the air. 1. If I take an iron tube (inside is air) and a speaker, 2. put the speaker at the beginning of a tube, 3. speaker is connected to frequency generator (with which I can change frequencies)...
  46. Superfluid universe

    I How is this formula for the speed of sound derived?

    c² = (n/m) ∂²U/∂n² where U = vacuum energy density as a function of the quasiparticle density n = quasiparticle number density m = bare mass of quasiparticle Is there a book, article where this formula is explained? Thank you.
  47. paulmdrdo

    Sound transmission underwater -- looking for equations TX --> Rx

    Hello! I have a system depicted below. I need to know what is the working equation that governs the transmit and receive power of the transmitter and receiver in the diagram. The transmitted signal is a sound wave and not an RF signal, the transmission is underwater. I would like to know what is...
  48. M

    Sources of Error in a Speed of Sound Experiment

    Homework Statement Determine sources of error which could have affected the results. Some background information: The lab consisted of playing a tone generated by a tone generator above a standing open-closed tube which had water in it. The first harmonic was measured through a computer system...
  49. Z

    Exploring the Relationship between Light and Sound: A Physics Perspective

    Why are sounds louder at night than during the day?
  50. K

    Sound waves produced by an aircraft

    Suppose that an aircfract somehow is not moving. Then I would expect the sound waves it produces to spread out uniformely in a spherical fashion. Now imagine a airplane traveling at approximately the speed of sound. In this case, if the airplane produces a wave at point A and after a time T the...
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