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. A

    Analyzing Sound Through a Rectangular Slot

    I am stumped analyzing the transmission of sound through a rectangular slot in a thin rigid wall. I have found online that a square or round aperture acts as a highpass filter with a 6dB/oct slope and a corner frequency where the wavelength is on the order of twice the aperture diameter...
  2. anonymous99

    Does the speed of sound depend on the speed of the medium?

    This means the sound wave reaches the outlet faster as it travels in the same direction as the medium. But I was reading online that speed of sound is independent of the medium so I don't know why my professor used this approach. If speed of sound was dependent on the medium, then wouldn't shock...
  3. N

    Fireworks Sound level at difference distances

    This is the work I've done so far... I=p^2/2dv...I=(10)^2/2(1.2)(343)=.12112 I(A)=P...(.12112)(4pi(500)^2)=380522.366 I=P/A...380522.366/4pi(4000)^2=.0018925 10log(I/I0)...10log(.0018925/10^-12)=92.77db 92.77-7(4)=64.77db I am winging it and that's the closest I can get to the right answer...
  4. T

    Adiabatic approximation in the derivation of the speed of sound

    The speed of sound in a gas at temperature T is given to be ## v=\sqrt{\frac{\gamma RT}{M}}##, where ##\gamma## is the adiabatic exponent, R is the gas constant and M is the molar mass of the gas. In deriving this expression, we assumed that the compression and expansion processes were so fast...
  5. R

    How to emulate the sound of a ringing bell?

    Summary: how to apply the the changes in frequency one can hear when a church bell is swinging through the air onto other acoustic sounds in a computer? Hello all, new to this forum. For an (art) sound installation I would like to apply the the changes in frequency one can hear when a church...
  6. K

    Waves: Calculate the sound intensity from two speakers

    Two similar speakers are connected to a stereo system that emits a signal of frequency 𝑓. However, the signal to speaker B is inverted so that positive voltage becomes negative (but with the same absolute value) and vice versa for negative voltages that become positive. A sound intensity meter...
  7. A

    Why Can a Sound Wave Not Travel Faster than the Average Molecule Speed?

    I am having trouble understanding the following passage in my physics textbook, particularly the bolded sentence: "The speed of sound in a gas is closely related to the rms speed of the molecules of that gas. In a sound wave, the disturbance is passed from one molecule to another by...
  8. D

    Sound dampened through an object

    1x10^-6 W/M2 is 60 dB The sound goes through both mediums --> 25dB *2 = 50dB lost Therefore the dound after object is 60dB-50dB = 10dB and converting to intensity it is 1x10-11W/M2 is that it?
  9. bubble-flow

    Oscillation of a particle inside water caused by a sound wave

    I don't really know where to start as this is not exactly my homework and I finished school some 15 years ago. I looked into my old high school notes, the last time I ever had anything about mechanical waves and sound. Unfortunately, we never learned anything about sound waves causing...
  10. D

    Sound power: What is 100mW amplified by 2dB?

    100mW = 20 dBm, that is then amplified by 2dB 20dBm/2dB = 10mW so power out of the amplifier would be 100mW+10mW =110mW?
  11. KiwiJosh

    Wavelength to Frequency Relationship in Musical Notes

    Hi people, So I've been digging into music theory and want to understand the basic reasons for how it is constructed. I've come across a particular relationship but I can't understand the reason it exists. A quick musical lesson: Imagine you've got a pure musical note: let's say C. From a low...
  12. KiwiJosh

    How Can Learning Piano Help Me Understand the Physics of Sound and Music Theory?

    Hi there, I am a guitarist and have recently decided to learn the piano as a tool for learning music theory. In digging into music theory I've come into wanting to understand it from the very physics of sound upwards. You'll probably find me on forums discussing sounds theory mostly! I live in...
  13. A

    Energy Received Physics of Sound question

    I'm not sure! I'm really lost on this problem to be honest.
  14. W

    MHB Forecasting metric using regression. Is this a sound approach?

    Hello, First post here. I have some data I am trying to do some forecasting on and was hoping somebody who knows what they're actually doing can verify what I have done. A few years ago, the company I work for developed a mobile app for its customers and about 1 year ago they added some new...
  15. A

    Sizing corner reflectors for frequencies in the audible range

    I'm contemplating extending the concept of corner reflectors to wavelengths in the audible spectrum, specifically road noise. I read somewhere that road noise is predominantly between 800 Hz and 1300 Hz. The corresponding wavelengths (at 20°C) are 16.9 inches and 10.4 inches. I read elsewhere...
  16. Indula

    What's an Ion's sound speed (Cs) in a plasma?

    Summary: Is it the same as Bohm velocity ? Is it the same as Bohm velocity ?
  17. S

    SciAm article: Trapping the Tiniest Sound

    Hi everyone! I honestly wasn't sure where I should put this, but I had recently come across this online article from Scientific American about researchers from NIST and the University of Colorado having developed the ability to trap and gain control of "phonons" (sound "particles", roughly...
  18. D

    Audio interference of sound waves from two speakers

    Homework Statement: Two identical audio speakers, connected to the same amplifier, produce monochromatic sound waves with a frequency that can be varied between 300 and 600 Hz. The speed of the sound is 340 m/s. You find that, where you are standing, you hear minimum intensity sound a) Explain...
  19. haushofer

    Sound waves: why do air molecules oscillate?

    Dear all, "Why do air molecules start to oscillate and influence each other such that a wave is forming when you hit e.g. a drum?" High school students asked me this, thinking the air molecules collide like marbles, creating a longitudinal wave. How would you explain this interaction-wise? Any...
  20. PainterGuy

    Pressure felt by a piston, Mach number of speaker making the sound

    Hi, Once someone wrote the following to me in response to my query. My query was somewhat unrelated to it and I don't even have the copy of query anymore. The pressure felt by the piston at any time is the average component of momentum of a gas molecule that is normal to the piston times the...
  21. snoopies622

    What causes that water kettle sound?

    When I turn on my water kettle, I hear that familiar "hush" sound as the water heats. What exactly is that? The surface of the water vibrating? Warmer, expanding air leaving the kettle? I know it can't be a function of the water temperature itself because when I turn the kettle off the sound...
  22. B

    Exploring Sound in Low Atmosphere: Speed, Intensity, and Frequency

    There is no sound in space because there are not enough particles to transmit the pressure wave. But what about really high in the atmosphere where there is just a little air? Would sound move faster, slower or at the same speed? Would the intensity (aka volume) go up, down, or stay the same...
  23. P

    How to solve this sound problem (minimum sampling rate required)

    Summary: The problem: If one wants to make a digital record of sound such that no audible information is lost, what is the longest interval, Δt, between samples that could be used? ( it gives a hint that humans can hear sound waves in the frequency range 20 Hz to 20 kHz. It should be a very...
  24. Borek

    Estimating Pitch & Volume of Collision Sounds

    I need to develop some kind of simplified formula that will allow me to estimate pitch and volume of a sound of two colliding objects in a simulation. It doesn't have to be exact, mostly it is enough that it follows the intuition - large object produce lower sounds, large and fast object produce...
  25. K

    Dimensional analysis (Speed of sound)

    I've been going round in circle and am stuggling as maths is not my strong suit. Any ideas? Up to the point where i equate the powers and then confuse myself, any help would be greatly appreciated.
  26. K

    Fluid dynamics and sound waves

    There are many fluid dynamics applications such as pipe flows, jet flows, boundary layers where we ignore any sound waves present in the system. I don't understand this though, because all sound waves are caused by pressure disturbances so why can we ignore these pressure disturbances when we...
  27. J

    SNR for an underwater acoustic signal

    Hi, I'm trying to model the transmission loss and SNR of an acoustic signal underwater. I'm using this expression to modelize the transmitted signal: y = sqrt(P)*exp(1i*2*fr*pi*t)' where P is the transmission power in watts, fr is the transmission frequency and t is the acquisition time. The...
  28. I

    Sound waves carrying mass and how to measure it

    I don't know in which category this subject belongs to. Anyways, here it is: https://www.sciencealert.com/a-new-study-backs-up-claims-that-sound-waves-really-do-have-mass-after-all?fbclid=IwAR2Cmsxm_Garm0PVn03f4UxVQ8adcK4Il3A_N7bUbJT1KaGR1ZfCbGuWVLE How exactly is this measured? Can we expect...
  29. K

    Trying to better understand sound & vibration on textured surfaces

    Hi, First thank you in advance for reading and answering my question. I am very much a newbie when it comes to physics, so while I feel my question in pretty straight forward I'm sure it's more complex than my thinking. OK so here it is... Does the texture of two surfaces change the decibel...
  30. J

    Intensity of sound, power output

    I is proportionate to E. r = 4.3xxm So I put 0.75I The answer is 49mW.. But I got 97.xxmW What is wrong?
  31. MermaidWonders

    MHB IPod voice memo is "playing" but no sound

    Hey! Thought I'd drop by and ask. Something strange happened this morning. I turned on my iPod because I was going to listen to a lecture recording for a class. I could get the voice memo to "play", but absolutely no sound is coming out. I tried it with and without headphones, but no luck at...
  32. NP04

    Frequency of sound in an open-open tube

    I do not understand parts c and d. For part C I have no idea where to start. And for part d, I got 1/4λ = L (open-close tube fundamental harmonics) so λ = 4L. But the answer key says it is 1/2 L. Help!
  33. G

    Calculating the Force of a Sound Wave on an Object

    Hello, I am going to be doing a project in which I'll be looking at how sound waves change the shape of an object. Specifically how sound waves can compress something. My question is, can I approximate a sound wave as a force in this case? I know a sound wave is much more complicated than a...
  34. C

    Why Does a Static Electric Discharge Make a Sound and Light?

    Since electrical charges causes a sparkle or a crackle which is light and sound. Also light and sound are forms of energy does that mean that electrical discharge releases energy and if yes then the release of energy have an effect on charge
  35. Dfpolis

    A How does Bell's 1964 theorem address detector independence and local realism?

    I have some questions about J. S. Bell’s famous theorem as presented in his1964 paper.1 These are about his theoretical assumptions and reasoning, not about experimental observations such as Aspect-type experiments. While some questions relate to the experiments, others do not because Aspect’s...
  36. F

    Huygens' Principle for Sound Waves

    I have a basic understanding of Huygens principle, but I don't quite understand why sound waves follow huygens principle. When sound travels, particles travel back and fourth in one direction, so how do sound waves end up traveling in all directions after traveling through a slit? Do sound...
  37. Mahathir

    Calculating Sound Power: I=P/A & Dependency on Area

    Is there any formula for calculating sound power? What does the A mean in I=P/A? Is the power of sound dependent on the area of its surrounding or something. I want to know if there's an equation for P like there's I=2π²a²f²ρv.
  38. L

    Why do things produce sound even though no pressure is applied to them?

    I understand that sound is a propagating pressure through a medium. We produced pressure and it’ll propagate through the medium as “sound”. How can we use this model to understand everyday-life experiences like opening a chips packaging and the packaging makes a sound, and alike. In the chips...
  39. Creed

    Finding out the speed of sound

    d² = 40² + 60² ---> I 60 = V.t ---> II 40 + d = V.(t + 1/8) ---> III Thanks in the advance. :)
  40. Miles123K

    3rd harmonic of a column of air with one end enclosed

    Homework Statement https://imgur.com/lGas78X The solution to this question says 450Hz. However, when I attempted to compute the frequency using the wave equation and find the normal mode solutions, I get 750Hz 2. Homework Equations I suspect that the solution could be wrong, is that the...
  41. F

    Can we hear beats between ultrasounds in the audible range?

    Hi all, I recently came across an exercise observing that human cannot hear ultrasounds, but could hear the beat between two different ultrasounds, provided that its frequency falls in the audible range between 20 Hz and 20kHz. The problem gives one frequency and asks for the range of the other...
  42. F

    Phase difference between sound waves

    I had to find the phase difference between sound waves created by two sources at different distances from a given point. I found the correct answer to be about 13.4. Would any other answer of the form (13.4 + 2npi) also be correct, assuming n is a non-zero integer? Or is 13.4 the only correct...
  43. Shea Thompson

    Help converting the NIST spectrogram of Calcium

    I am not a physics major and don't know even where to start trying to interpet this spectrogram from the NIST website of the element Calcium https://physics.nist.gov/PhysRefData/Handbook/Tables/calciumtable2.htm My goal is to find a way of converting this spectrogram into a tone or frequency...
  44. jybe

    Sound Interference Problem -- Observer moving between two speakers

    Homework Statement Two identical loudspeakers are driven in phase by the same amplifier at a frequency of 680 Hz. The speakers are 4.6 m apart. An observer stands 9 m away from one of the speakers as shown. The observer then starts moving directly towards the closest speaker. How far does the...
  45. S

    Sound Wave Problem -- time of flight in air versus in water

    Homework Statement Homework Equations v = d/t Solve for t. t = d/v The Attempt at a Solution In my General Physics 2 course we are doing sound waves I have the answer to the problem which is 90.8m I am trying to understand the concepts of sound wave. So please correct me if I am wrong, 1...
  46. G

    Sound Wave Interference Problem

    Homework Statement This is just a question about a question in Serway & Jewett's "Physics for Scientists and Engineers 3rd Ed". It's Objective Question 3 from Chapter 18, building on Example 18.1 from the text. Two identical loudspeakers placed 3.00 m apart are driven by the same oscillator...
  47. G

    Stress, Strain, and Sound in a Projectile Steel Rod

    Homework Statement .[/B] For a certain type of steel, stress is always proportional to strain with Young's modulus 20 x 10^10 N/m^2. The steel has density 7.86 x 10^3 kg/m^3. A rod 80.0 cm long, made of this steel, is fired at 12.0 m/s straight at a very hard wall. a) The speed of a...
  48. Cc518

    What is the Maximum Wavelength for Constructive Interference of Sound Waves?

    Homework Statement Two in-phase loudspeakers, which emit sound in all directions, are sitting side by side. One of them is moved sideways by 3.0 m, then forward by 4.0 m. Afterward, constructive interference is observed 1/4 and 3/4 of the distance between the speakers along the line that joins...
  49. D

    Why does a higher density slow down sound in air?

    Homework Statement Sorry, it's not an actual problem, it's just a statement I don't understand from my text - "The density of water vapor is less than that of dry air. Therefore, the higher the humidity (that is, the more water vapor there is in the air), the lower the density of the air. For...
  50. X

    Speed of a sound wave (compressibe flow)

    Hi, there is no particular question that I need help on, just something my lecturer told us in lesson which I couldn't quite understand so i'd like to check my understanding on this. I know that the speed of a soundwave is 'c' in undisturbed flow. Suppose the flow velocity is 'U'. If the...
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