Questions tagged [acoustics]

Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. Applications of acoustics are for instance the audio and noise control industries.

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How, if, does the inside air of a football influence it's motion?

And before me lies a football. Say it's filled with pressurized air. If I kick it, how will the inside air be influenced? Will the kick induce soundwaves? Can the ball give a sound? Will it influence ...
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Is possible to "isolate" some audio frequency? [closed]

I want to know if is possible to "isolate" some audio frequency for certain human that only this human can hear this "frequency spectrum", some animals can hear certain frequencies ...
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1 vote
2 answers
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How does one apply the phase change of $π$ on reflection at the rigid end of a string?

Consider a string, with a free end $P$ and another end $Q$ which is rigidly fixed. Now, we start oscillating the point $P$ (with $0$ initial phase difference) and a wave starts traveling(in the ...
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Can Low-Freq sound wave with High-Amplitude destroys human ear?

Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz. So that's mean human unable to hear 1 Hz frequency sounds since it's far under 20 Hz. At detectable frequency of human like ...
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Could a Haptic Actuator change the natural frequency of an object?

Could a Haptic Actuator which can operate in the 10 - 500hz frequency range be used to modify a wooden objects natural frequency?
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3 votes
2 answers
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How can you change the resonant frequency of a solid guitar body?

I am trying to figure out if it would be possible to change the resonant natural frequency of a solid-body guitar. For example, let's say it resonates at 100 Hz and I want it to resonate at 200 Hz. Is ...
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2 votes
4 answers
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Does the standing wave equation proof require $\ell=Nλ$? [closed]

Consider two identical sources $S_1$ and $S_2$ of waves, separated by a distance $\ell$ (as shown in the figure). The sources produce waves in opposite directions(and towards each other). Now, ...
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2 votes
2 answers
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Why does an antinode form at the open end of an organ pipe?

I recently learnt about reflection of waves in various media and the resultant standing waves formed. In a string which is tied at an end, the wave formed reflects with a phase difference of 180 (at ...
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The speed of time [closed]

If the speed of light is 14,545.075 x the speed of sound, could the speed of time (and/or gravity) be 'something' like that times the speed of light, say 2,705,384,023.877 m.p.s? (Sonic boom > ...
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1 vote
2 answers
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Can we tell anything about the velocity at which a spherical stone falls into a lake based on the sound it makes?

Suppose we have a spherical cow... I mean stone, and we throw it to a lake. Can we tell anything about the velocity (speed and angle) at which it falls based on the sound it makes? And based on a ...
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Which procedure could help decide whether a string's total length has a separate effect from the tension?

My AP physics 1 exam is tomorrow. This question is from a practice exam I have but I never really understood the answer Using the setup above, a student tests how the tension in a string affects the ...
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How to calculate the overall harmonics of a system of tubes?

Let's say there is a tube closed at one and and open from the other. The open end is connected to another tube (of smaller diameter) which is open from both ends. How can I calculate the overall ...
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What is volume of sound?

Is there another term for (volume of sound)? What is the relation between intensity and sound volume?
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Convert noise measurements that used 3-dB exchange rate (ER) to 5-dB

NIOSH uses 3-dB as the exchange rate (ER) for sound measurement, while OSHA uses 5-dB as the ER. Is there any way to convert the measurements using these two approaches? If yes, how can we do that? I'...
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6 votes
4 answers
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What frequency of cord shaking maintains the same vertical motion for a point on the cord after increasing the wave speed on the cord?

I'm studying for my upcoming AP Physics 1 exam but can't figure out this problem A student shakes a horizontally-stretched cord, creating waves. The graph above shows the vertical position $y$ as a ...
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3 votes
1 answer
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What is the displacement amplitude of a 140 db sound wave?

I am teaching a unit on sound in my upper elementary science class, and my students are curious about how far air molecules are actually being displaced in a sound wave. I told them that if the air ...
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Frequency and length

Why is pitch inversely proportional to length of an instrument? I think i know meaning of frequency but if anyone can also explain frequency according to higher level physics it shall be great.
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3 answers
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Why can we hear instruments but not voices?

I've seen this graph: But I don't get something. Consider the 2kHz line (highlighted in red). This graph implies we can hear an orchestral instrument at 2kHz before we can hear a human at the same ...
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Speed of sound in a real gas

The speed of sound in a real gas is $C = \sqrt{ZkRT}$, where $C$ is the speed of sound in the gas, $k$ is adiabatic gas constant $={C_p}/{C_v}$, $R$ is the gas constant and $T$ is gas temperature in ...
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Does air column change its frequency to one of its modes as and when needed?

The question might make it sound like I'm considering air column to be a conscious entity kinda thing, but what I really mean is, Say I've a tuning fork ringing and I bring it near a test tube with ...
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2 votes
0 answers
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Numerical methods for modelling non-linear pressure wave propagation in fluids/solids

So far, I only have experience solving the Laplace/(inhomogeneous) Helmholtz/Maxwell equation with boundary conditions using the boundary element method (BEM). So far I have used open source tools for ...
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1 vote
1 answer
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Why the prongs of a tuning fork have different oscillation phases?

I've been reading many questions about why tuning fork has two prongs. Many of them explain that each prong oscillates with opposite phases. As a consequence, the compression and decompression of air ...
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Regarding derivation of Acoustic wave equation

Is it correct to start deriving the acoustic wave equation by assuming the speed of the fluid at every point is very small ?
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2 answers
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What causes this strange noise in a pair of walkie-talkies?

Let us suppose that Bob and Alice both have walkie-talkies. They are both 3m apart from one another. Alice pushes her walkie-talkie to speak but instead of speaking, she starts walking toward Bob. ...
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2 answers
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Does a thin sheet of water reflect sound just as well as a thick layer of it?

It is very difficult to hear underwater sounds from above the surface of a body of water. This is suggested to be due to the speed of sound being very different in air versus water, leading to most ...
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1 vote
1 answer
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A question about progressive sound waves

I know the value of $s(x,t)$ in a given pair $(x,t)$, how do I know the value of the pressure variation in this same pair $(x,t)$? Knowing the maximum displacement $(s_m)$, the speed of sound in this ...
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Why exactly do higher frequency (>240 Hz) sounds on Mars travel ~4% faster than lower frequencies? What's the physics and are there optical analogies?

SciTech Daily's April 1, 2022 Variable Speed of Sound on Mars: What Sounds Captured by NASA’s Perseverance Rover Reveal About the Red Planet says The result of the recordings: a new understanding of ...
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What is the difference between velocity of wave and velocity of pulse on a string wave?

I have read in my textbook that velocity of a wave remains constant but then there was a question to find velocity of pulse as a function of x in a vertically hanged rope.(where x is the position of ...
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2 votes
2 answers
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What prevents a "beam combiner" from being able to cancel out energy?

I understand that normally when two waves combine destructively this happens only in certain places; the energy doesn't disappear but is redistributed to other places where the interference is ...
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"Proper Branch Cuts" in A Physical Problem

I am solving the following acoustic problem. Consider a two-dimensional duct bounded by two parallel walls separated by a height of $H$ as shown. The duct is filled with air. A vibrating piston(...
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1 answer
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Sound of string in a guitar

I study about waves and I learn that the velocity of a transverse wave in a string depends only on the tension and the density of the string. The frequency depends only on the source (whatever ...
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7 votes
3 answers
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What physical state of a wound string corresponds to a 'tuned' string?

Many instruments can be strung with strings comprised of a solid core and wound with another metal wire, e.g. the viola. I was wondering about the physical state of wound strings when they are 'in ...
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1 answer
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Motion of non-homogeneous string fixed at both ends when pulled at a point

How to solve displacement and velocity profile of string which has density $d_{1}$ till distance $x$ and density $d_{2}$ from $l - x$ to $x$ fixed at both ends and when given initial displacement and ...
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2 votes
1 answer
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Is the sound speed and density relation different for compressible and incompressible media?

I'm studying "speed of sound in air" and I read that sound speed is inversely proportional to the density of the medium. However, I also know that sound travels fastest in solids, and that ...
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Why does not the speed of sound in air depend on frequency and wavelength? [duplicate]

I have read that speed of longitudinal waves depends upon the frequency and wavelength and, but why it doesn't happen with sound waves in air? And if velocity of sound doesn't depend upon the ...
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2 votes
2 answers
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Does the speed of sound wave change when the source velocity change?

The speed of sound in air is about $740$ miles per hour. Suppose that a police car is sounding its siren and is driving towards you at $60$ miles per hour. At what speed is the sound of the siren ...
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Uncertainty of frequency from tone generator app on phone

If I were to download a tone generation app (sonic) on my phone (Iphone 13) and use it to generate a sine-wave of a certain frequency, what would the uncertainty of the frequency be? How can it be ...
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1 vote
0 answers
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Transduction coefficient of an electromechanical system

I have been recently doing a physics experiment which requires me to determine the transduction coefficient of a speaker system, undergoing electromechanical resonance, in an AC circuit. The quantity ...
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0 votes
1 answer
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Long wavelength limit of sound wave

I often heard the statement that the deformation of the system corresponding to a sound wave in the limit $k\rightarrow 0$ must go over into a displacement of the system as a whole. I don't understand ...
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15 votes
4 answers
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Can sound waves deform (curl brake) like water waves?

As far as I understand, both water waves and sound waves are mechanical waves, in the sense that both are created by the relative movement of particles in a certain medium. Sound is propagation of ...
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0 votes
0 answers
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Why does sound travel faster in helium than in air? [duplicate]

Sound wave travel faster in solid than in liquid, and travel in air with the slowest speed because solid is denser than liquid and liquid is denser than air. So, sound wave speed should be faster in ...
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Numerical solutions to the 3D wave equation

I am doing a research to explore the existing numerical schemes that are used to solve the $3$D wave equation. The standard form of the problem in $3$ dimensional setting is : $$\Delta u= \frac{1}{c^2}...
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-2 votes
4 answers
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I have seen people define frequency or amplitude in two ways, which one is correct?

I have a doubt on frequency and amplitude,I have seen people define these things in 2 ways,for instance, people define frequency in mainly 2 ways,if we draw a pressure-position graph of a sound wave,...
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39 votes
7 answers
5k views

How do headphones and earphones produce good bass if tiny speakers can't produce low frequency sounds very well?

It's a well known fact that small/tiny speakers cannot produce low frequency sounds very well. Conversely, large speakers cannot produce high frequency sounds very well. Hence the need for tweeters ...
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7 votes
3 answers
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What is the frequency of the sound?

Can someone tell me what is the frequency of the sound waves? Is it the number of compression or rarefaction going through in a second or the number of vibrations of the particles of the medium ...
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0 votes
1 answer
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We say that speed of sound is fastest in solids because particles are closely packed to each other, but why is speed more in hot air?now,they are far

I know we say that the speed of sound is most in solids because the particles are closely packed to each other,so,the energy transfer can take place easily compared to when they are farther in air or ...
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0 votes
2 answers
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Why does the amplitude not increase the speed of the sound wave?

The way I see it,if there's a set up A which has 5 particles and another set up B which also has 5 particles,and assuming everything else is same in these set up,like distance between particles etc,if ...
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1 vote
1 answer
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Why is this acoustic scattering integral a Fourier transform?

I am puzzeled about this part in the book "Acoustic Absorbers and Diffusors" from T. J. Cox, P. and D'Antonio. It describes the scattered pressure from a surface of a pressure source in ...
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2 votes
2 answers
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Why doesn't pressure affect the speed of sound in air? [duplicate]

I keep getting the answer "because density increases when pressure increases" but that doesn't really make sense to me since in denser materials - like water - sound travels faster. And if ...
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1 vote
1 answer
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Hand damping of a vibrating string or membrane

Problem is the following: If I have a guitar string or a drum membrane which is vibrating (and thus creating sound), when I place my hand or finger on it looses energy quickly, and eventually ...
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