# 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. ### I Sound power, amplitude, frequency, and decibels

Hello, It has been difficult to find a clear answer to this question. I've found some sources stating that the power of a sound wave depends upon both amplitude and frequency. I've found other sources stating that the power of a sound only depends on amplitude. I've found sources stating...
2. ### Understanding MIT's applet on sound with Fourier coefficients

Here is an applet for playing around with Fourier coefficients and sounds. Here is a document explaining a bit about the applet. I did not quite understand everything. Let me go through it. Sound as perceived by humans is the physical phenomenon of variations in air pressure near the ear...
3. ### I How long would a tuning fork vibrate in vacuum?

[I do not know if this is the right subforum] The answer to the question to the title is: for very long time. However the tuning fork clearly has to stop at some point because some of the energy will turn into heat. However I want to quantify for how long. More specifically I am interested on...
4. ### B Log relationship between thickness of material and sound absorbed?

So I have done an experiment on the amount of sound energy absorbed based on thickness of pvc foam, and found a logarithmic relationship between the two. I've used the frequency-dependent acoustic attenuation power law, which is derived from stokes' law. Frequency-dependent acoustic attenuation...
5. ### Measuring the Velocity of Sound in this Lab Exercise

Here is the exercise: Which one seems logical and correct ? this one: [ Normally when we increase distances, the velocity of sound decreases?] Or this one? You might wonder why. Well, my friend in class told me that the second table could be correct because the experiment was conducted at...
6. ### I Relationship between frequency and power for sound?

Hello, I have a problem wrapping my head around the relationship between frequency, power/pressure, and displacement. Let's say I have two sine waves that I generated in my computer: A 50 Hz tone and a 100 Hz tone. Let's say they both have an amplitude of 1. Therefore, they will both have...
7. ### Power output and sound intensity

In the picture below
8. ### Measuring the Speed of Sound in Water, Using Faraday's Law

Hi! This project involves both mechanical and electrical elements, so I'm discussing it in this forum since I'm not sure which one it would fit better into. I'm working on an experiment in which I'm trying to measure the speed of sound through water. The approach is simple: I have a long...
9. ### Where Can I Find Doppler Effect Sound Samples for Specific Scenarios?

Hi, I am looking for some sound clip examples of the doppler effect for some specific questions. Specifically I would like to find a single tone/horn recorded in the three different ways: 1. Not moving at all 2. Moving past the recorder at a slower speed 3. Moving past the recorder at a higher...
10. ### Speed of sound from resonant length of tube vs tuning fork wavelengths

The graph is, I do not understand why how it is possible to find the speed of sound from the gradient for this graph. Can someone please help? Many thanks!
11. ### B Conversion of Potential Energy: Sound or Heat?

When a coin is dropped from a certain height and collides with a glass surface, is the majority of the potential energy converted to sound or heat? And how would one determine this as I only hear the sound and cannot measure the significant change in temperature?
12. ### The Physics of Light and Sound

I brought time over to the other side and multiplied to get 686 m/s but that wasn't correct
13. ### Sound Varieties: Rules for Varying Ranges

It seems that a sound (eg aa, ah, ih...) has a variable range of sound.I know that the before is affected by the follow, eg ''d" in do and did are different. Are there any other rules for the variation range?
14. ### I How is the damping of sound (over distance) affected by air properties?

Hey all, For my physics major I need to quantify the acoustic effect of sunfields. I'm trying to do this by measuring the sound level before and after a sunfield, and after that by measuring a comparable situation, only without a sunfield. By comparing the results of the two measurements I'll...
15. ### B If I double sound on my PC, how would the sound intensity increase?

If I have on my PC let's say sound on 50% and I increase it on 100%, how would the sound intensity change? Would it be twice bigger? But I think that function of sound intensity level dependent on sound percets is a linear function, isn't it? How to explain it? Why is it the linear function?
16. ### Correct statement about sound wave

My answer is (1) and (2) but the teacher said it is only (1). I thought the speed of point at center of compression and center of rarefaction would be the maximum. Or the correct one is the speed at center of compression and center of rarefaction would be zero? Thanks
17. ### B Destructive Interference in the sound of multiple firecrackers set off at once?

There is a massive and continuous fireball as fire crackers are exploding, generating thousands of shockwaves. Perhaps they are bouncing off each other and cancelling each other out like noise cancelling headphones,
18. ### Why doesn't helium have any effect on the sound of my voice?

How did you find PF?: By searching for a answer to my question and everyone only knows how helium effects the sound of their voice not mine.No one has a a answer to the question why doesn't helium have any effect on the sound of my voice? My question that no one has a answer to and ignores the...
19. ### Sound card sampling rate 1.2msps?

I am designing an experiment for pam-ook which acquires a radio audio signal to the mic input of my laptop. I process the signal using c++ code employing an audio library (PortAudio) which provides the data stream. I require a sampling rate of 1.2msps but the sound card in my laptop has a...
20. ### B Question about Stereo Sound while listening to a Song by the Beatles

Eu estava ouvindo The Beatles, a música "Yellow Submarine". Percebi que os instrumentos e os vocais saíam de fones de ouvido diferentes, os instrumentos do lado esquerdo e os vocais do lado direito. Gostaria de saber: Como isso acontece? E como é feita essa separação entre vozes e instrumentos...
21. ### I Understanding Sound Waves in Fluids: Pressure and Velocity Fields

When we talk about sound waves in a fluid (air, water e.t.c.) we mean that the pressure ##P(x,y,z,t)## satisfies the wave equation, the so called velocity field of the fluid ##v(x,y,z,t)## satisfies the wave equation or both?

23. ### I Does high humidity air transfer sound better than dry air?

Does high humidity air transfer sound better than dry air?
24. ### Writing: Input Wanted Does this sound like a rip off of Halo?

Does this sound too close to being a rip off of Halo. By the 23rd Century, a special component spread out over the Naval Defense Force, Ground Defense Forces, and United Space Force is SPARTAN or SPecial Assault opeRations TeAms Network. SPARTAN is broken up into 10 Units, the GDF has 5, the...
25. ### I How is the sound horizon at recombination and BAO measured in the CMB?

So I'm trying to understand the sound horizon measured at recombination and the sound horizon measured with BAO. Here is what I've gathered (PLEASE tell me if I'm wrong and if you could please explain, I've been trying to read but can't find a clear explanation): ~r(z*) is measured using CMB...
26. ### I Sound Frequency & Pipe Wall Thickness

We have 2 open metal tubes, made of Stainless Steel. They both are the same length of 1 metre, and and Outer Diameter of 76mm. One pipe has a wall thickness of 1.5mm, and the other has a wall thickness of 2.0mm. It was our reasonable guess that the tube with 2.0mm wall thickness, should...
27. ### B About actually touching something and sound made by collision

https://futurism.com/why-you-can-never-actually-touch-anything/amp We know the friction happens because of the intermolecular forces between the atoms of the surfaces in contact. When we place something on other there are places where they get come in contact there are bonding formed and due to...
28. ### I Can ground albedo near a highway refract noise upward?

I live near some highways that are roughly "a couple of miles" away. On some blessed days they are inaudible, and on other days they roar with a low frequency sound that penetrates into every corner of the basement. (If frequency matters, it would be most preferable to refract sound at 20Hz...
29. ### Direction of of the velocity vector for particles in a sound wave

Using the equations mentioned under this question, I came up with following analysis and directions of velocities on either side of ##x_1##. Also, I'm not sure if there is an easier qualitative way to know the velocity directions rather than do a detailed Calculus based analysis?
30. ### Reflection of sound wave in an open organ pipe

I know that standing waves form in an open organ pipe. Since, standing waves can only form from superposition of original wave and reflected wave, so there must be a reflected wave in an open organ pipe. But I fail to understand how sound wave can reflect at the open end of organ pipe.
31. ### Physics behind the sound of guitars

(a) When a taut string is plucked with a finger then it starts vibrating with a transverse wave pattern in the string, which causes the air particles in the immediate vicinity of the vibrating string to oscillate. These oscillating air particles will result in a sound wave traveling in 3...
32. ### MP3, WAV, FLAC or APE: which one has the better sound quality?

It seems to me though WAV files are heavier than the others in bytes it has the best sound quality. It's interesting since nowadays you can download more quickly (who knows perhaps this is also a lie... :cool: ) files, so why bother for MP3 or FLAC, the good old WAV file is da best! Unless of...
33. ### I Equivalent formula for a Sound wave in a medium like an EM wave

1.) In electromagnetics, wavelength in a medium is $$\lambda = \frac{\lambda_{0}}{n}$$, where $$n$$ is the refractive index. What is the equivalent formula for sound wave in a medium? 2.) Is there a reference sound velocity, like electromagetic wave speed in vacuum is c_{0} =...
34. ### Question on sound intensity and dB

Would we have to use the 3-dB exchange rate? How would we solve this question?
35. ### I Help Designing a Resonance Box for Tuning Forks

I got these tuning forks from someone. However, I do not have the resonant box for amplification of the sound. I decided to get it made so that I can experience the fundamental frequency (and other harmonics) more clearly. I am planning to provide this design. In summary, the box would be...
36. ### Why is the speed of sound used here? And is this correct?

If two people are holding a stick going from the Earth to the moon and the one on Earth pulls the stick, would the person on the moon feel it immediately? This question was answered on Quora and the answer given involves the speed of sound and claims that the person on the moon would not feel...
37. ### Solving a Sound Wave Equation in Physics 1: Halliday, Resnick, and Krane

Homework Statement:: This is from 5 ed, Physics 1Halliday, Resnick, and Krane. page 428 about sound waves I have highlighted the equation that I don't understand. How did the author get it? I understand how they get from the middle side to the RHS of the equation, but I don't understand how...
38. ### B Simple Acoustics Question -- Which neighbor hears the other better?

There are two blocks of apartments separated by a narrow alleyway. Person 1 is in the middle of the room in Apartment 1 (first floor if you are in the UK and second floor if you are in the USA!) and Person 2 is on the ground outdoors in the alleyway. If both people speak at the same volume...
39. ### I Micro Sound Waves: Can 1 Hear What Only Another Can?

Are there soundwaves so tightly packed that you could have two people standing next to one another and fire sound at a distance directly into one person's ear as that only that person hears it?
40. ### Resultant Frequency and Wavelength of Interfering Sound Waves

##-w1## and ##-w2## are to shift the cosine graph to the right, and ##\frac{2pi}{\lambda}## is to stretch the graph. But I can't seem to draw an appropriate ##y1+y2## graph (quite irregular) and I struggle to find the resultant frequency and wavelength. Also, why is there angular frequency in a...
41. ### I Sound and apparent wind -- Any Doppler effect?

If two cars are driving side by side at the same speed, their relative speed is zero but do they nonetheless perceive a sound Doppler effect from the other car's siren because of the apparent headwind generated by their speed?
42. ### I How does sound reflect from an interface at an angle?

How does sound reflect from interface at an angle? The propagation of light is determined by a single factor - index of refraction. Sound is affected by two factors - speed and acoustic impedance. Take the case of two substances with identical acoustic impedance but different sound speeds - one...
43. ### I Does this defense lawyer's probability argument sound like BS?

Either that, or the author is a typical "pop scientist" author that doesn't understand probability too well. https://nautil.us/issue/4/the-unlikely/the-odds-of-innocence
44. ### Sound waves inside an inert gas fusion reactor

Hey, its that under educated guy again, I hope the mighty big brains can spare me my feelings. Anyways, I saw this toy that levitated a ball of water using nothing but sound waves. So naturally I tried to apply this to a plasma and fusion. Using a inert gas reactor, or a fusor for that matter or...
45. ### I Sound between two rooms - closing which door affects the sound most?

Imagine you have two identical rooms opposite each other with some space in between. (Ie two rooms across from the passage or two rooms leading off of another room). Sound is being emitted from one room only. Would closing the door in the room where the sound is being emitted from or would...
46. ### Investigating the Sound Reflector of a Gas Inlet Tube

My theory is that the gas inlet end, which is supposed to act as a sound reflector may not be doing a great job because it is plastic and has a hole cut in the centre for the gas inlet port. But by that reasoning, the flames at the end most distant from it (the sound inlet end) should be the...
47. ### The English word that hasn't changed sound or meaning in millenia

Gregory Guy, a professor of linguistics at New York University, has a favorite word - lox. “The pronunciation in the Proto-Indo-European was probably ‘lox,’ and that’s exactly how it is pronounced in modern English,” he says. “Then, it meant salmon, and now it specifically means ‘smoked salmon.’...
48. ### Variation of the Speed of Sound in metals under tension

In a block of metal, each metal has a characteristic speed of sound. When metal is under tension, such as a guitar string, the speed rises as the tension increases. How does the speed vary (in a block say) as a function of tension along each of the three axes? I am assuming that transverse...
49. ### Location of the particles when 1.5 periods of a sound wave have passed

qn iv. I understand that when 1.5 periods pass, every compression will become rarefaction, and every rarefaction will become compression(someone please correct if wrong) but the answer key shows something else. I'm interpreting the answer key drawing to be 1 compression and 4 rarefactions...
50. ### Sound Engineering: Why's it so hard to get things like timbre right?

Apologies if wrong forum. Could not see anything about acoustics. Is this mathematics? Why's it so hard to get things like timbre right? Digitised instruments and voice changers don't always sound right. I had a chance to visit a recording studio. Was given a lengthly talk about sound from a...