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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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 ...
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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 ...
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15 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?
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53 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 ...
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1answer
12 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 ...
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332 views

Speed of sound in air

Quick question. I thought that the speed of sound in air was constant, say in the right conditions of pressure and temperature, and humidity... 300 m/s. Now, if I have a sound source that moves ...
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184 views

What is the exact physics behind sonic levitation

Me and a group of friends decided to choose sonic levitation as our research topic. However, after looking up the theoretical background, we hit a roadblock: (Here is an image of a standing sound ...
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20 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 ...
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3k views

Why and how is sound produced when two objects hit each other?

When two objects collide and undergo a partially inelastic collision (so every one we experience in every-day life), they rebound to a certain degree, but kinetic energy is not conserved. Thus, the ...
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3answers
102 views

Does sound have a “louder” direction?

I have a question about the propagation of sound waves. We have two TV's in our house that are almost right on top of each other. One is located on the first floor and the other one is located on ...
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20 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 ...
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27 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 ...
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56 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 ...
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104 views

Can sound be used to change trajectory of objects?

I'm doing a fictional history in near future, where there is a very advanced army but i like to keep things real, and my knowledge of physics is very limited...but i know sound has been used to ...
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1answer
25 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?
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23 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 ...
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16 views

Find the diameter of the tube and frequency of resonance [closed]

A tube of a certain diameter and of length 48 cm is open at both ends. Its fundamental frequency of resonance is found to be 320 Hz. The velocity of sound in air is 320 m/sec. Estimate the diameter of ...
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1answer
695 views

Resonance and natural vibrations in vacuum

In my Physics textbook, it says that if two pendulums of the same natural frequency are placed next to each other and if one is set into vibration, the other starts resonating and when the first one ...
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1answer
1k views

Is it possible to use “negative sound waves” to “cancel out” a sound to create silence?

I saw youtube videos that claimed to do this, although I'm quite certain the videos just excluded sound and lied. However, I am wondering if the physics of this is actually possible - to create a ...
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26 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 ...
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2answers
69 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 ...
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1answer
26 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 ...
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1answer
153 views

How does a sonic black hole (or dumb hole) work?

I came across this term and I heard they used sonic black holes to detect something analogous to hawking radiation, but I have failed to find sources which explain how exactly they work and how they ...
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203 views

different liquid in a container produce different sound

Does the type of liquid in a container affect the sound it produces? example like milk, water and coffee produce a minute different sound
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20 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 ...
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2answers
501 views

Do asteroids create sonic boom while entering the atmosphere?

Because of the lack of any materials to propagate sound, it can't spread in space. There's the air in the atmosphere, but its volume mass increases constantly (either linear or exponential, I don't ...
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450 views

Relation between pressure and particle displacement in an acoustic wave

Consider an acoustic wave in some medium, expressed as particle displacement: $$s(t,x) = e^{j(-\omega t + kx)} $$ I understand that pressure must be at its maximum when the particle displacement is ...
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277 views

Why do we hear a higher pitched sound outside the water when we smash two stones in water?

The observer is outside the water; the stones are in water (say, 1 m below the surface). This produces a higher-pitched sound for the observer than if both the observer and the stones are in air. Is ...
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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 ...
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15 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 ...
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5k 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 ...
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3answers
36 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, ...
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1answer
44 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 ...
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23 views

Is there an acoustic Black Body Radiation?

Imagine a cavity in a infinitely extended solid filled with another type of solid in thermal equilibrium. Are there statistics for phonons equivalent to the Black Body Radiation by Planck?
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375 views

Resultant frequency if 3 harmonic notes (a chord) is played

If I know the frequency of individual notes being played (let's assume D, F# and A), how do I determine the final frequency if they are played (nearly) simultaneously as a chord. To put the problem ...
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1answer
125 views

Why am I not hearing frequencies of range 14 kHz-15 kHz? [closed]

Recently, a Radio Station (Red FM, 93.5) started a campaign called "RED FM bajao Machar Bhagao" (English: Play RED FM, scare away mosquitoes). In this, they claim to be broadcasting some frequencies ...
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1answer
55 views

I made a tin can phone using a plastic slinky and paper cups. Why didn't it work?

After watching some videos on Khan academy in regards to the information theory, I spent a few minutes creating a primitive "tin can phone." The materials of my phone are a plastic slinky and two ...
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2answers
35 views

Two supersonic planes. Do they hear each others sonic boom?

Plane A is traveling at Mach 2 and is over taken by plane B traveling at Mach 3. Does plane A hear the sonic boom from plan B? If so when? Does plane B hear the sonic boom from the slower Plane A? ...
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1answer
181 views

Sound Propagation using Finite-Difference Time-Domain (FDTD) considering wind effects

I am trying to plot the propagation of sound from a fixed source in a 2D environment using Finite-Difference Time-Domain (FDTD) Method taking into account the effects of the wind velocity. I came ...
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3answers
369 views

Why do magnets silence anvils?

Today I've been to a forge. The blacksmith demonstrated that if he beats the anvil without a magnet attached, it make horrible noises. As soon as he reattached it, the sound of the anvil was way more ...
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40 views

What are the proper unit types for the calculation of the frequency of a tuning fork? [closed]

Wikipedia Article on the subject The formula states that the calculation of the frequency with cylindrical tines should be $$1.875^2/(2\pi L^2)\times(Er^2 /(4P))^{1/2}$$ where the variables are ...
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1answer
3k views

Why, when one opens 1 car window, does that noise occur?

When you're driving and you open 1 car window, say the front one, there comes a horrible noise, but when you open another window just the slightest bit, this noise goes away (I'm sure most people know ...
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1answer
37 views

Car window vibrating noise

I was going to ask a question similar to: Why, when one opens 1 car window, does that noise occur? but saw that it was already asked and answered very helpfully. However, there are a couple other ...
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1answer
91 views

What is the physical origin of acoustic modes in a duct?

Lets deal with wave propagation in a cylindrical duct. We ask the question: "what is the general form of a pressure wave which can propagate through the duct?" In answering this, we assume that the ...
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1answer
84 views

What is causing the Trumpet Sounds that are emited from the sky?

In these last years, a phenomenon have appeared in several countries (US, Canada, Australia, Russia, Germany, and others). It consists of sounds like a trumpet coming from our own planet's sky. ...
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1answer
62 views

Can sound waves be made to project 3-D shapes, like a reverse sonar? [closed]

Can sound waves be manipulated to project 3-dimensional shapes or forms, like a reverse sonar?
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2answers
11k views

How sound intensity (dB) and sound pressure level (dB) are related?

Source: http://www.engineeringtoolbox.com/sound-power-intensity-pressure-d_57.html Both sound intesity and pressure level are measured in dB. Given a specific sound, are these two dB values the same? ...
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233 views

Using sinusoids to represent sound waves

Having some free time, I've begun a mini-project attempting to understand how music works in more detail, which has so far only involved music theory and a bit of set theory. I'm now trying to get my ...
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35 views

Books about musical acoustics

Apart from physics, I love music and I want to learn about musical acoustics. I know some things, but the problem is that most of musical acoustics books are written for musicians. That means that ...
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How quickly should a fluid come to hydrostatic equilibrium?

Let's say I'm holding a one-liter water bottle, full of water, which I then drop. Before dropping the water bottle, the equilibrium is for there to be a pressure gradient in the water canceling the ...