# What is Sound waves: Definition and 332 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 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...
2. ### B What sound frequencies can pass through a hole in a wall?

Hello, First of all, I will try to overcome language barrier as this is not my native language and the more topic is scientific - the more chance for me to get lost in translation. Apologies for poor grammar in advance. I marked it as Advanced post, so apologies if this has to be corrected by...
3. ### Why does a series of pulses generate a pitch?

Here's the thing: the ear detects a pitch by splitting a sound wave into it's frequency components in the cochlea, which is in a way a spatial Fourier transform (ish...) But I never liked this analogy because it doesn't explain why I hear a pitch when a series of pulses entern my ear. A single...
4. ### I Why singing a note while playing a note creates a difference frequency

If you play a note of a certain frequency on a flute and simultaneously sing a note at a different frequency, then you create a third frequency that wouldn't be there if you play or sing in isolation - and the frequency of this subharmonic is the difference of the flute frequency and the voice...
5. ### I Summing and averaging RMS pressure (amplitude) of sound waves

Hello, I've been trying to wrap my head around why, if given the sound pressure levels (dB1 and dB2) of two uncorrelated sounds, if you want to sum them together, you sum their intensities using the equation: 10 x log10(10^dB1/10 + 10^dB2/10). Likewise, if you want to average them, you average...
6. ### I Understanding the propagation of sound on molecular Scale

I am actually an undergraduate in Physics but I didn't understand this basic phenomenon. I saw this youtube video today and I was wondering how molecule in air would be able to regain it's initial position after it has transferred it's energy to the adjacent particle. Is it like a rebound, it...
7. ### Misc. DIY 'ECG' Machine: Testing Feasibility of Wave Transference

I'm trying to make a DIY 'ECG' machine, except that it'll only record heartbeats on a piece of paper. Basically the piece of paper will be wound round a cylinder like object, which will be being spun slowly by a motor. A pencil at the end of a stick or something will be writing to this piece of...
8. ### 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?
9. ### I Acoustic wave properties and momentum

I have read about doppler effect in acoustics so i searched for the relation ship between wavelength of wave produced by linear movement of body and its momentum along with other dependent variables such as density of fluid (leaving acoustics for a second) and temperature but souldn't find a...
10. ### Same frequency sounding different

I was always thinking that frequency decides the type of sound we hear ( ex: high pitched squeaky sound). But then I read somewhere that loudness i.e. intensity can also affect the sound we hear. Still the quality of sound should depend only on frequency since loudness would simply make it more...
11. ### 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?
12. ### 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?
13. ### 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...
14. ### I A Question About Shock Waves From an Airplane

The elementary treatments I've seen show the shock wave spreading out in spheres centered on the plane and growing in radius at the speed of sound. So, clearly, the shock wave is sound, but what sound? What is it the sound of? In order for the plane to give off sound, it has to be making a...
15. ### 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...
16. ### Superposition of the sound waves from two speakers

Wavelength = 2L = 80cm
17. ### B Apparent missing negative phase oscillation energy - where is it?

When an oscillator produces waves - let's say they are highly focused - that are damped by a second negative phase oscillator, where is the wave energy? The energy in each set of waves must still exist. Has it become hidden?
18. ### Signal Transmission Using Sound Waves

Consider the following thought experiment... You are an engineer with a very peculiar assignment. With a mind to reduce the investment of excessive human labor and material waste, you have been asked to build an apparatus similar to an old-fashioned voicepipe. You are asked to ensure that the...
19. ### Amplitudes of longitudinal sound waves

I'm coming back to physics after a long so apologies if this has a basic answer- How can the amplitude of a longitudinal sound wave be increased without increasing its wavelength? I understand what it would look like graphically if a low amplitude sine wave and high amplitude sine wave were...
20. ### Sound waves affected by wind/sound waves in materials

Are sound waves in air affected by wind? If the medium of the air propagation travels forward, does the sound also travel faster or is the sound simply vibrations in positions of space which disregard the movement of its medium. Would a transverse wave similarly move faster? If I was to...
21. ### Formula for calculating the wavelength of sound in interference

Here is a diagram of experiment: Here is the results: Average distance between nodes (cm) Frequency (hz) Line 1 Line 2 Line 3 500 253 176 105 1000 333 438 None My analysis: ƛ/2=D ∴ƛ=2D where ƛ=wavelength (cm) D=distance between nodes/antinodes (the average,cm) 500hz: Line 1...
22. ### Formula for calculating wavelength of sound waves in interference?

The values calculated was nowhere near the theoretical values, though I guessed they won't be as the results recorded was incredibly inaccurate. My teacher acknowledged the fact the final values won't be close to the theoretical ones but also said that my formula was wrong, that it works to find...
23. ### Different Loudness Sound Waves and Destructive Inteference

Summary:: Can smaller volume sound waves completely cancel out larger volume sound waves, and if not to what degree will the larger sound be canceled out. Hello everyone, just had a question regarding destructive interference. So I am in the process of writing/designing a sci-fi/fantasy power...
24. ### 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...
25. ### 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...
26. ### 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. ### 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...
28. ### 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...
29. ### 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...
30. ### 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...
31. ### 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).
32. ### 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...
33. ### 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...
34. ### 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...
35. ### 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...
36. ### I Need to Calculate the Speed of Sound for a Lab

Homework Statement Calculate the speed of sound in the classroom. You can use: Tuning forks, water, beaker, pvc pipe, ringstands, etc. Homework Equations v = f(wavelength) For fundamental frequency: L = 1/4(wavelength) For fundamental frequency: f = v/4L The Attempt at a Solution Here is...
37. ### How do sound waves interact when two radios are facing each other?

So again, I’ve got this analytical question on my mind and it’s been bugging me for a couple weeks now. So my question is, how do sound waves work? I’m talking about if you put two radios facing each other playing different songs. What would happen? Is it if waves match then they just combine...
38. ### Sound Intensity Propagation and Sound Waves

Hello everyone, I'd ask you through an illustration which for me would be more clear to put questions I wrote in the image: Thanks to all! Cheers Luigi
39. ### Calculating Clicks: Spoke Card Oscillations and Rotational Motion

Homework Statement A thin card produces a musical note when it is held lightly against the spokes of a rotating wheel. If the wheel has 32 spokes, how quickly must it rotate, in revolutions per minute, in order to produce the A above middle C (i.e. 440 Hz)? Homework Equations ω=2πƒ; ƒ=1/T...
40. D

### Difference between Ultrasonic waves and sound waves.

Hello everyone, Can I seek help on the difference of ultrasonic waves and sound waves? I find it confusing.
41. ### Do light and sound waves roll up and break like ocean waves?

When sea waves approach the shore they roll up and break due to different velocities of water layers formed due to the gradual change in water depth. The highest wave peaks move faster than all other layers and thus falls down. All other layers fall the same way but in a delay. this ends up with...
42. ### High frequency being transformed to a low frequency

Hi Physics, I have an idea but before i start. I must know am I right. Is it possible? We have a small room with two objects. The first object is a producer of sound waves out of the human hearing range. This object sends ultra sound waves to the second object. The second object start to...
43. ### A Question about Sound Waves Propagating Through a Large Metal Cube

Okay, I have a very simple question that...Suppose we have a very wide cube(dense and hard)...We place two persons at each of its ends...One the persons strikes its surface at one end. Now this person A will hear the sound due to vibrations of that end's surface (which further vibrate the air...
44. ### Can sound waves cause a burning effect on some materials?

Hi, I wonder is it possible sound wave heat material that high that the material goes up in flames? Or what other type of frequency can make some materials burn?
45. F

### Sound Waves -- propagating, dispersing, volume effects?

Generally sound waves are depicted as simple sine waves, where volume is related to amplitude, and there is periodic motion. Realistically sound waves aren’t as simple. I attached a picture of a dissipating sound wave. I would appreciate if you guys could answer a couple questions I have about...
46. F

### Are Non-Sinusoidal Sound Waves Just Magic?

Are real non-sinusoidal sound waves, such as square sound waves, always composed of sinusoidal waves? I know that non-sinusoidal sound waves can be created with an infinite number of sinusoidal sound waves as described by Fourier series. Of course real non-sinusoidal sound waves cannot be...
47. ### Can someone explain to me these equations of sound waves?

A bomb explodes on Mars how long will sound waves to travel from Mars to earth?? Ans= 0sec?? or any other answer needs only little hint
48. ### Sound Waves in Different Mediums

Homework Statement 1) When sound waves travel through increasing temperature, what increases, frequency, wavelength, or both? 2) When you inhale helium and then your voice becomes high and squeaky, what causes this to happen? Homework Equations Vsnd= √(γRT/ M) vsnd= λf The Attempt at a...
49. ### Diffraction of Sound Waves Through Slit

Hi there, I have a scenario in which different frequencies will be played behind a curtain with a 2m opening. I would like to calculate the angle of diffraction for different frequencies played by the piano. One equation that I came across through research is Fraunhofer's Single Slit equation...
50. ### Can someone explain to me these equations of sound waves?

I = 1/2 ρ v ω2 A2 I don't know what "I" is nor do I know what "A" is but it has to do with sound waves. May you also please correct me if I am wrong but is: ρ = density of air v = velocity of sound = 343 m/s ω = angular frequency of the sound wave = 2πƒ And also may you please answer what is...