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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Slinky reverb: the origin of the iconic Star Wars blaster sound

This is a fun problem that I came across recently, which I'm posting here for your delectation. We all love a good slinky: they can be used for all sorts of fun demos in physics. One example is the "...
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Lethality of sounds and extreme “loudness”

In theory, could pure sound be lethal? How loud would it have to be? Also, which events are the loudest in the universe, and how loud are they? I'm confining attention to events which occur regularly, ...
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Is there a naturally occuring sound pressure level reference?

There are lots of devices that purport to measure the absolute value of sound pressure levels. Here is an example, here's another, there's also this iPhone App. Putting such devices side-by-side in ...
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Polarization of sound

Sound can't be polarized because the vibration of such type can't be polarized i.e, it can't be limited or controlled by any barriers and so polarization is not possible in them. This is what my ...
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448 views

Rolling sound of thunder

When sound of thunder travels to the listener from its location,different parts of the same wave have to travel through air of different moisture levels,densities and molar masses. This is what I ...
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292 views

Why do cold metal plate make less noise?

I have a metal gate in my home so I have noticed that when it is a hot day and if I hit it it makes a lot of noise but when there is a rainy day and the weather and the gate re cold and if I hit the ...
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In terms of the Doppler effect, what happens when the source is moving faster than the wave?

I'm just trying to understand this problem from a qualitative perspective. The Doppler effect is commonly explained in terms of how a siren sounds higher in pitch as it is approaching a particular ...
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641 views

How to determine frequency components present in distorted signal, with the set of possible components already known?

I am trying to choose the best approach to digitally analyse a signal, which is a mix of an unknown number (but less than 16) fundamental signals at specific frequencies (e.g., sines). The goal is ...
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302 views

Waveguides (in the ocean?)

The speed of sound in the ocean is given by $$c_s(\theta,z) = 1450 + 4.6\theta - 0.055\theta^2 + 0.016z$$ $\theta$ is the temperature in degrees celcius, and $z$ is the depth. In a simplified model, ...
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476 views

Would a phone move upon vibration in a completely uniform situation?

I was sitting down yesterday and saw my phone vibrate on a side, and it moved about a centimetre per vibration. I wondered why it moves, and thought perhaps that the side it was on had a slight slope,...
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293 views

Accelerating faster per second than the speed of sound?

What would happen if you were to accelerate one end of a material, say a steel rod for instance, at faster per second than the speed of sound in that material? For example, if the speed of sound in ...
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253 views

How does one find the wave velocity and the phase speed?

While I was studying beats, I tried to find a displacement function of any particle in the most generalized form. I ended up with $$y=2A\sin(\pi(t-x/v)(f_1+f_2))\cos(\pi(t-x/v)(f_1-f_2)).$$ Now, ...
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Maximum delay for effective active noise cancelling?

Active noise cancelling reduces unwanted sound by sending the inverted phase of the original phase: (Source: Wikipedia) Theoretically, this seems logical to me. However, in real life, the anti-...
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857 views

Whistling on bottle tops

It is well known that if you blow horizontally on a bottle top it creates a sound. Pouring water to the bottle changes the pitch. I have been doing experiments on the relation between the sound's ...
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Frequency of a Tuning Fork

Question: Which of the following affect the frequency of a tuning fork? Tine stiffness Tine length The force with which it's struck Density of the surrounding air Temperature of the surrounding air ...
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Independence of frequency in sound waves?

Why does the frequency of sound wave depend only on the source? Why is the frequency and not any other "quality" independent of everything but the source? And that said, why is velocity and ...
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411 views

Water excitation with sine waves

I saw that video when they connected a water hose to a speaker emitting 24 hz sine wave, and its illusion on the shape of the follow going out of the hose (because the video capture rate is fixed at ...
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553 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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Acoustic Metamaterials: Negative Bulk Modulus?

In acoustic metamaterials we have simultaneously negative bulk modulus, $\beta$, and effective mass density, $\rho$. I understand how one can obtain a -ve $\rho$ by constructing a solid-solid system ...
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313 views

Sound as a conserved quantity

From the first man to the present day men, all of them have made some sound. Sound is an energy, it can neither be created nor can it be destroyed. Therefore, every word spoken by each human that came ...
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Can someone explain how water from a garden hose can propagate in a sine/cosine wave?

A video posted on Youtube. How does this phenomenon work? I know he is using frequency to propagate water in a sine/cosine wave, but how does it exactly work this way? Why do we see it as if its ...
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2answers
148 views

Calculating the mass equivalency of a song?

I've recently become fascinated with the idea of sound energy having a theoretical equivalent mass. I've read over this thread: Do light and sound waves have mass I understand this part: $m_{eq}=E/c^...
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Can light waves cause beats?

My question is pretty brief. When two sound waves of nearly same frequencies interfere, we get beats. But, I have not observed something like that happening in the case of light. In fact, most of the ...
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Why it happen's when I rub my finger's? [duplicate]

I have a pc with a metallic body on my CPU case. Yesterday suddenly the earthing wire of my CPU broke down and I was able to feel a little bit current on touching it's metallic body. But what I found ...
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396 views

Sound of packing tape dispensation?

I am sitting in a cigar lounge, and under the jazz music playing I can hear this strange, rising and falling tone, that sounds similar to one of those weird tubes you can find at a fun fair. You tilt ...
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125 views

Acoustic wave equation for a closed sphere

I am looking to model the nodal surfaces in a resonating closed sphere. The sound source is external. What sort of wave equation will reveal the spherical harmonics depending on the frequency, speed ...
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audio signal arithmetic

BACKGROUND: I have been messing around with audio signals in Audacity and realized that by inverting a signal and adding it to the same signal I get no signal. Thus (S + invS) is really (S-S). (S+S) = ...
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Whistle Physics

I'm looking for a simple explanation of how a whistle operates. I know that forcing air over a sharp lip can set up a wave in a resonating cavity, but how? "Most whistles operate due to a feedback ...
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338 views

Sound Wave Propagation: Why HF are more specular while LF are more omni

The propagation of high frequencies sound waves is more directional (specular), and they don't diffract as much as low frequencies. Low-frequencies diffract and thus propagate in a more omni-spherical ...
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2013 Russian meteor event, Sonic Boom or Explosion Boom?

In the lastest meteor event in Russia there was a big BOOM heard long after the meteor had passed. In this youtube video we can see at 4:30 the Meteor passing.. then hearing the BOOM at 7:00 , 150 ...
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Calculating displacement amplitude of ultrasonic power transducer

I am not a physicist, but my current project drives me to some physics-related computations, hence seeking help. I have some ultrasonic transducers, 5938D-25LBPZT, for which very limited information ...
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469 views

Can a sound mathematical formula become a science theory?

Can a sound mathematical formula become a science theory if it is constructed using a pattern creation process from sense-data, applied to observations by an inductive mapping, in contrast to ...
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260 views

Active speakers picking up cellular tower waves?

Since a week or so a constant high pitch sound (~4khz) emanates from my active monitor speakers. After eliminating any ground or power source issues I noticed, that the sound rises in volume whenever ...
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Does sound propagate further in freezing weather?

A few days ago I went for a walk in the evening. We're having winter with a little snow and freezing temperatures. We're in a quiet, shallow valley with a train station about 1km from us. I heard a ...
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Ultrasonic wave through air

I am not a physicist but I am extremely interested in this area. The simple version of my question is: "What is the maximum range of an ultrasonic wave traveling through air?" Now, I know it depends ...
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742 views

Reflection of sound waves

I was doing a physics experiment, and i encountered a question which i couldnt answer. The experiment was about using a radar technique to measure the speed of sound. The apparatus was a plastic tube ...
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Orthogonality of modes

I want to know what it exactly means when it is said the modes of vibration are Orthogonal.I understand what it means mathematically but what is its physical interpretation?
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How does sound travel in space?

In relation to this question: How can a black hole produce sound? Which notes that the hole "produces" sound. The top answer states that: What you think of as the hard vacuum of outer space ...
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What information is stored on gramaphones/tape recorders/CDs/DVDs

I'm a Software Developer by profession and my physics knowledge is limited what I had learned at high school level. Please excuse me if the question is trivial. Question: From what I know, a sound ...
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224 views

How come vibrations?

We all know that sound sensation is produced only when sound waves reach upto us. We all know that sound waves are disturbances propagating in air, Vibration is necessary for the generation of sound, ...
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How can a black hole produce sound?

I was reading this article from NASA -- it's NASA -- and literally found myself perplexed. The article describes the discovery that black holes emit a "note" that has physical ramifications on the ...
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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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How much information about the scale of a waterfall can be obtained from its sound?

Is it possible to constrain the height, volume flow, or distance of a waterfall from the quantitative analysis of a high-quality recording of its sound? As an aside, the simulated sounds of fluid ...
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Does altitude affect sound pitch?

Due to differences in air pressure, temperature, and other factors, the speed of sound varies with altitude on Earth. Does this affect the pitch of the sound in any meaningful way? For example, if I ...
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41 views

How is the wattage of a human larynx calculated?

This site says the typical human voice has a wattage of about 1W. Another site indicates it is 80db with about 0.001W of energy. I'm confused. How does one compare 80db of 0.001W against 1W? Most ...
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617 views

What determines the pitch of a resonant object

What determines what pitch an object such as a bell or tuning fork produces when struck? I have heard that the box in the "king's chamber" of the great pyramid at Giza is tuned to 438 Hz. I know that ...
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558 views

What properties define a good resonator?

In my question "Resonance in a 1 ft granite box", someone answered that my granite box (a one foot cube) would make a very poor resonator, which makes me ask what characteristics make a good resonator?...
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Resonance in a 1 ft granite box

I have a granite cube made using 6 slabs of granite 1 foot square and 1 inch thick. The top and bottom slabs have a 1 inch margin around the edge. The slabs are just set together, not notched or ...
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What's the difference between photoelastic constant, photoelastic coefficient and the acousto-optic coefficient

I'm reading a few papers about how the optical properties of materials change when a under stress or a force acts upon them. I seem to be encountering the following three terms: Photoelastic ...
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Does clipping to $m$ guarantee a maximum peak-to-peak amplitude $m$?

There is a technique called clipping in sound synthesis. It is explained on Wikipedia . I make music and like this technique: You make an extreme "fat" noise, maybe with a lot of resonance, but then ...