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.

learn more… | top users | synonyms (1)

1
vote
1answer
73 views

Why are exploding HHO bubbles louder then pure HHO?

We tried my electrolyzer with a friend today, we filled a small bottle with HHO gas, and set it on fire. It was loud but not a big deal, like a firecracker. Then we added some soapy water and created ...
1
vote
1answer
48 views

Mach Number after Normal Shock

Is there any way that someone can give me more of a conceptual explanation for the fact that the Mach number downstream of a normal shock must be less than or equal to 1? I understand the ...
13
votes
1answer
2k views

Why are ultrasounds used for producing images of body organs?

Low frequency waves can penetrate better than high frequency waves, then why are high frequency waves used in ultrasounds for sharper images? Similar is the case in detection of flaws in metal ...
0
votes
1answer
27 views

Reverberating sounds?

I know a home where there are two television sets in two different rooms. The TV sets are diametrically opposed to each other. When I move from one sound source of TV one to TV two a phenomenon ...
1
vote
3answers
98 views

Physical interpretation of source term in wave equations

Let me start with an example. If we base our calculations on the Newton's second law without any further mathematical treatment, then our equation describes equilibrium of forces, i.e. it is of the ...
1
vote
0answers
48 views

How would I calculate the frequency of the sound produced by a bowed glass plate?

I'm working on a project that involves getting a note to sound from a glass plate by bowing its edge with a violin bow. I'm trying to work out exactly what frequency I'll get from a piece of glass of ...
0
votes
1answer
62 views

What's the relationship between the tension of string and the decay rate of its vibrations?

It seems that the more tension on the string, the more slowly the sound would decay after being plucked. Is there a formula relating the two? How is it derived?
5
votes
1answer
50 views

Overtones of Bells Over A Distance

The hourly bell tower sound at Indiana University Bloomington sounds like a higher frequency when heard from ~1.4 km away, compared to standing right next to it. Is this effect likely due to the ...
0
votes
1answer
34 views

Properties of infrasound of our muscles?

I have read, that some animals (like cats) are able to hear other animals (like humans) staying still by percepting infrasound, emmited by their muscles. Is this true? I know, muscles are really ...
0
votes
1answer
44 views

Pitch and loudness relation

Using an Oscillator in a program, I noticed that the lower and the higher frequencies are less loud than the middle ones. I suspect there is a relation between pitch and loudness but can it be ...
0
votes
1answer
84 views

Intensity of sound vs Speed of sound

I am finding out the relationship between intensity of sound and speed of sound. To do that, I am using this equation: $$I =\frac{∆P^2_{\rm max}}{2ρv}$$ where ∆P max = Pressure amplitude, I = ...
2
votes
1answer
34 views

What is the equation of motion for multiple simultaneous pressure waves in a medium? (In the context of stimulated Brillouin scattering)

My overall motivation is to derive the behavior of Brillouin scattering in a birefringent fiber. Brillouin scattering is a nonlinear interaction between light and sound. In classic Brillouin ...
0
votes
3answers
63 views

In a sound wave, is there rarefactions at both ends?

I was reading my book Physics, For scientists and Engineers, Third Edition, by Randall D. Knight, studying the first chapter on waves. This diagram is provided on page 565: The diagram is easy to ...
2
votes
1answer
51 views

Sound when traveling faster than sound

I was wondering, if I am running at the speed of sound while playing music on my iPod will I be able to listen to my iPod while running at the speed of sound? or we cant hear anything while running at ...
1
vote
2answers
124 views

What is meant by thermal penetration depth?

What is meant by thermal penetration depth? I am doing a project on Thermoacoustics. while researching I came across about thermal penetration depth.I searched over the net but i didn't get a clear ...
3
votes
1answer
64 views

Where exactly is the antinode of an air column with open-closed boundary conditions?

Suppose that I have an air column with closed-open boundary condition. The air pressure at the open end of the tube is constrained to match the atmospheric pressure of the surrounding air. ...
3
votes
2answers
66 views

Sound in stirred hot fluids

If a hot beverage in a cup gets stirred, the sound of the spoon changes. You can easily hear this if you repeatedly cling the spoon to the cup ground after stirring. The cling sound will raise in tune ...
0
votes
1answer
62 views

Relationship between sound pressure level and amplitude of signal

I have a loudspeaker. Let's say that I feed a signal to it, say, a pure sine wave: $$f(t) = a \sin(\omega t).$$ How does the sound pressure of the resulting sound relate to the amplitude $a$? Is ...
0
votes
2answers
29 views

Undamped oscillations of sound wave

I read in google that When we hit some metal or object, then a sound is generated by that object. If we hit that object with more force, then we can hear a sound of more amplitude than previous one ...
0
votes
1answer
87 views

Why velocity potential?

(Aero-)Acoustics (among other parts of fluid-dynamics) loves the velocity potential $\varphi$ defined as $\vec{v} = \nabla \ \varphi$ with the condition of $\nabla \times \ \vec{v} = 0$. I am ...
2
votes
4answers
124 views

Why is perceived sound intensity based on a log10 scale?

Decibels are logarithmic with a base of 10. I've been told before that two car horns are not twice as loud as one car horn. Rather, it takes ten car horns to be twice as loud, because of the log10 ...
0
votes
1answer
33 views

Can we tune the exhaust system of a gasoline car to be as quiet as an electric car? [closed]

Electric cars are quiet, so quiet that legislation is proposed in many countries, to make them audible to pedestrians, for obvious safety reasons. My question: is it possible, without getting into ...
0
votes
1answer
40 views

Can you record sound through vacuum? Like this: (object)(vacuum)(object)

There are these videos on youtube that play sound of Jupiter for example: http://www.youtube.com/watch?v=e3fqE01YYWs Does anyone know if this is real at all? How can you record sound through vacuum ...
2
votes
1answer
42 views

What information do we lose when we increase whale songs to our hearing range?

TV documentaries on marine life often feature the evocative sounds of whales communicating with each other (apparently), over very long distances. The frequency of baleen whale sounds ranges from 10 ...
2
votes
4answers
203 views

Speed of sound in vacuum

I am not a scientist but I have a question about speed of sound in vacuum. All I know is that the speed of sound $v$ in a medium is given by formula $$v= \sqrt{\frac E\rho},$$ where $E$ is elasticity ...
0
votes
2answers
66 views

Grand Canyon Sound Problem Troubles

Yesterday, I got a question in class, this is the question: If you shout into the Grand Canyon, your voice travels at the speed of sound (340m/s) to the bottom of the canyon and back, and you hear an ...
1
vote
0answers
87 views

Wave equation - Cases where separation of variables doesn't work

Separation of variables combined with the Fourier's theorem is the most common technique of solving D'Alembert's wave equation: $$ \Delta\Phi-\frac{1}{c_0^2}\frac{\partial^2 \Phi}{\partial t^2}=0 $$ ...
2
votes
1answer
342 views

Why can we hear sound better on the water than on land?

If we sit in a boat on a lake we can often hear people talking on the shore clearly in contrast to sitting in an empty field and hearing the people talk over the same distance. I heard that this ...
1
vote
1answer
123 views

Influence of acceleration in acoustic doppler's effect experiment

Recently I've done an acoustic doppler's effect experiment for physics lab assignment. The setup was two microphones in a straight line, movable object with sound source and a pc with the usual sound ...
2
votes
2answers
80 views

How can the choice of wood make a good violin?

We always hear about some really fine and expensive wood that is used to make guitars, violins and other musical instruments. What's the physics behind this? What parameters (e.g. bulk modulus etc.) ...
4
votes
1answer
184 views

Using a laser to overhear a room conversation

Movies with science based tricks and gimmicks are generally silly and sometimes even annoying. The science based trick that I don't know enough about to judge is the following (and I have seen it in a ...
4
votes
2answers
58 views

Refraction, diffraction or reflection of human voice

Why is possible to hear in an open space someone's voice even if he's not facing me? Is it because of refraction, diffraction or reflection of the sound wave?
0
votes
2answers
30 views

Does background noise while strumming a string affect the frequency recorded?

Does the interference of the waves cause instances of destructive interference where there is no amplitude. Technically the wave is still there although its amplitude is 'cancelled' out but those ...
0
votes
1answer
99 views

Do two waves of different frequencies create a resultant wave of lower frequency?

In my results for testing background noise, i found that while strumming a guitar in: a noisy area, the frequency picked up by the mic was 352 Hz while in a quiet area, the frequency picked up by ...
1
vote
2answers
43 views

Interference of two waves of different frequencies relevance to background noise + sonometer

If two sound waves of different frequencies are recorded then does the interference between the two waves of different frequencies alter the resultant frequency recorded. In better context, I'm ...
0
votes
1answer
40 views

Directional subwoofer?

I was thinking. The subwoofers that I've seen are a circular parabolic surface section (or perhaps a circular circlic(?) surface section?) and are considered omni directional. I would guess that ...
1
vote
2answers
47 views

Is there a version of “delayed choice” for sound waves?

I'm familiar with the uncertainty principle in harmonic analysis, which states that you can't localize the support of a function in both the time domain and the Fourier domain. One of the physical ...
3
votes
2answers
157 views

Why speaker beeps when a cellphone is kept near it?

Once I had kept my cellphone near a computer speaker. After some time, a call came over my phone. Strangely, the speaker started humming and beeping till I received it. Why did the speaker started ...
0
votes
1answer
16 views

Why would the acoustic absorption coefficient of hexane in air be less than air?

Why would the acoustic absorption coefficient of hexane in air be less than air? That is, a 120kHz pulse train shows a bigger amplitude after traveling in a hexane/air mix than in pure air? My ...
2
votes
1answer
54 views

Aerodynamic noise created by cooling fan

What is the reason behind the noise created by fan blades while moving? Some paper says that it is because of the Kármán vortex street but it can be formed in static bodies only. Most of the ...
0
votes
1answer
86 views

Is there a mathematical relation between the volume of a speaker diaphragm and the intensity of sound it produces?

I am trying to find out how speaker cones of different diaphragm volumes will produce a certain intensity of sound. Is there a relation that could be used after the volume of the cone has been found?
2
votes
0answers
69 views

Finger snapping: Maximum fingertip speed and generated pressure change

The wikipedia page for finger-snapping (or finger-clicking) describes the physics thus: There are three components to the snapping finger sound: (1) The "friction" or "sliding" sound between the ...
2
votes
2answers
180 views

Is it possible to measure temperature using sound?

Is it possible to measure the temperature of something using sound, by blasting sound waves at solid objects, liquids and gasses, then measuring how much sound is reflected or absorbed, to give an ...
3
votes
1answer
34 views

What is the Optimal Separation Length for the Tines of a Tuning Fork?

I'm building tuning forks (for fun... why not?), and among one of the design decisions is how far apart should I place the tines (the two long prongs) from each other. I'm not entirely certain whether ...
0
votes
1answer
40 views

Hearing sound when going supersonic

Suppose we are travelling supersonic along a straight line. Further up along the line, there is a stereo, that's emitting sound at a frequency that changes in such a way that the Doppler shift caused ...
1
vote
0answers
110 views

What is the relationship between the velocity of an object and its Sound Intensity Level in an inelastic collision?

Assuming the mass, acceleration, and height of the dropped object are constant and the area of the measured sound wave is constant, would the relation be linear, exponential, logarithmic, square root ...
0
votes
0answers
33 views

Why do acoustic lenses need air channels?

In every design of an acoustic lens I have seen so far, be it Fresnel lens or GRIN lens, there are always air channels included in the design. I don't see why this is needed. Couldn't a lens be built ...
26
votes
4answers
6k views

Is a bomb's shockwave strong enough to kill? [closed]

I'm watching a movie, The Hurt Locker, and the first scene shows an IED explosion which kills a soldier. Of course movies don't depict explosions with maximum realism, but I noticed the debris and ...
0
votes
3answers
124 views

Pitch range and size of wind instrument

Looking at wind instruments, there is an apparent relation between the size of the instrument and the pitches it can produce; The larger it is, the lower pitches it produces. The question I have is, ...
0
votes
1answer
56 views

Reproducing electricity [closed]

We all know reproducing solar energy is possible. Same stands for mechanical energy (air, water, coals) - they are all reproducible. But what about other types of light ? A diode light for example ...