Acoustic Definition and 150 Threads

Hi, I am looking for a more precise calculation for determining an accurate end correction for an open-ended pipe of a relatively high fundamental frequency and am hoping someone might be able to steer me in the right direction. Researching online I have found the general calculation of...

Hi there, I should probably know this (attempting to do a PhD in physics!) but is there a way to differentiate between longitudinal and shear acoustic waves in a solid? I know that seismologists know which is which by using the time of flight difference for the two types of waves and the...

I am supposed to have a qualitive knowledge of acoustic peaks for my exam, so none of the maths. After reading around I am still left with a few questions. Is the first acoustic peak from the acoustic oscillations at last scattering? I imagine there were many oscillations before then but we...

Hi ! I need your help ! I have been kind of stuck with the following problem for a few days : I made measurements on a plate radiating sound with an accelerometer and I found very low values of displacement(1-10 pm !). It seems very very very low (less than 1 atom !) Depending on the...

Hello, can anyone clarify what's the principle (or physics law) according to which small objects are kept suspended in air in acoustic levitation devices? I understood that the device essentially creates an acoustic standing wave inside a container. This means that, in some specific regions...

A friend of mine and I were having a discussion about acoustic resonance. He theorized that a building could be destroyed by acoustic resonance. Where I disagreed. Thinking that a building doesn't really have an acoustic resonance because of its non-uniformity of being brick and mortar...

Dear all, Searching proofs for Dark energy, people always mention "the first acoustic peak in CMB". can anyone tell me what exactly is that? how long did we expect it to be and now -having Dark energy- how long do we see it? can anyone help me please?

Hello, I am using stepper motors for some neuroscience experiments on rats. The problem is that our experiments are being corrupted by high-frequency noise. The acoustic frequency of the noise is high enough that humans can't hear it, but rats can (humans can hear up to 20 kHz, whereas rats...

Have a project to do on an acoustic resonance chamber, a loudspeaker attached to a perspex box with a copper pipe, there was a microppohne inside the chamber connected to oscillloscope. We investigating a few variables in most detail was route [1] [1]damping by chainging materials in the...

Hi, was just wondering if anyone could help me out with this query, I'm just curious to know why high frequency acoustic waves are greatly absorbed underwater? Thanks in advance.

Hi, everyone, I have a question about the acoustic wave equations in two different forms (see the attached). I think the simpler form is more general (in terms of density variation) than the complex one, although the latter looks more general at first sight. But my advisor thinks it's the...

Hello all, Ive never really worked with Acoustics before but have been looking into acoustic raditation, effects in cavitation, acoustic fields, sonar, etc. However, it has been pretty difficult to find any information on equations or modeling of the collision of the acoustic waves. The...

Hi, I have been looking to finding the energy of an acoustic sound wave. I keep looking, but its not the exact equation I am looking for. I am look for an equation of how much energy is present in a sound wave and how it changes over distance. Does anyone know?

Hi I have some confusion in understanding the acoustic contrast actor . You can check wiki if you are not familiar with the term. http://en.wikipedia.org/wiki/Acoustic_contrast_factor If there is a foreign particle in the path of a sound wave (to be specific Standing wave for my...

Dear all, This problem is on the modeling of an unfocused receiving acoustic transducer and compute the electric signal due to the pressure field. I have come up with this simple model in 2D. Basically, the transducer has a flat surface S and the surface is assumed moving in the direction...

What exactly are Baryon acoustic oscillations? How do we detect them? How are they used to build a "ruler" of cosmological parameters? How are BAOs related to the late time ISW effect? and to dark energy? Lots of questions, hopefully someone here can give me some answers or at least some...

Dispersion Relation: w2=B(1/m+1/M)+-SQRT[(1/m+1/M)2-(4sin2ka/mM)] For waves on a diatomic row of masses, what is the physical meaning of acoustic and optical branches of this dispersion relation? What is the expression for the maximum frequency of the optical branch? Really stuck on...

It's very hot in the UK at the moment, and so I went out and bought a semi-industrial 20" pedestal fan for my living room. It certainly does its job in cooling, but unfortunately, it also sounds like a jet engine. This got me wondering. I assume it uses a standard brushless electric motor to...

Acoustic "Frequency Hole" -- How does this work? Here is a project proposal that I read: http://amasci.com/freenrg/audhole.html I decided to give it a try and I made this project and it works. But I don't seem to understand why and how this works. Can someone explain this phenomenon...

Homework Statement Suggest how the energy difference arises between the optic and acoustic branches in a 1d diatomic chain.Homework Equations The Attempt at a Solution I know that on the optic branch atoms oscillate in anti-phase within the unit cell and in phase in the unit cell on the acoustic...

I am looking for an introductory book on sensing using acoustic emissions. Specifically, I am hoping to use acoustic emissions signals to detect tool wear (and classify the wear as mild, severe, etc.). Does anyone have a recommendation? Something with examples using LabView and/or MATLAB...

I am currently doing an acoustic experiment, testing the sloshing noise made by the fluid content in a tank. My software and microphone gives me all the outputs from the sloshing noise but not the loudness calculation. I am needing a figure for every test to key into my statistical software and...

Hey! I understand frequency calculations in tubes, open ended or closed, however what would you classify a tube ring? Imagine a rube ring brushing against something constantly, if the tube was static and it made contact with something, you'll get waves traveling around in both directions...

Homework Statement Derive p(r) = \frac{A}{r}e^{j(\omega t - kr)} from pV = nRT Homework Equations The Attempt at a Solution From ideal gas law I have p(r) = \frac{nRT}{V} R and T are constant, so I can pull them out now and replace them with A. If V is the volume of a spherical shell of...

Set-up Closed tube with a hole at each end. Microphone at one end attached to computer. Clap noise made at the other end which will produce a range of frequencies. The computer program detects the resonant frequencies and their amplitudes. The graph produced seems to show the lower resonant...

HI! I am actually working on a project involving Acoustic Modem. However, we met up with some problems. We actually took the acoustic modem from another item. Thus there might have been some programming done to the modem which we do not know. The acoustic modem will work when its...

http://www.aes.org/tmpFiles/elib/20091022/12398.pdf A ribbon loudspeaker consists of a rectangular element of aluminum foil suspended within a magnetic gap and clamped at its ends (ie a clamped-clamped beam). Current is applied to the foil, which produces an electromagnetic field that...

Hi all, Through my tears, I'm trying to compare two acoustic emission sensors. The first sensor has a specification that says its sensitivity is −150 dBre 1V/μPa. The other sensor says its sensitivity is -70 dB ref 1V/μbar. (Note the different units.) Wikipedia tells me that 1 Pa = 10-5...

Hello everyone, I'm trying to put together a computer program that will convert codes into sounds that can be quickly and accurately picked up by the human ear. For instance, it needs to take "0048" and turn that into a sound, that will be different from "0049" or "1148", and a person...

Does anybody know the acoustic properties of carbon fiber. I've used google extensively but I've had no success. Is there a well known reference book within the materials engineering realm that gives the sound absorption coefficient (also known as the Noise Reduction Coefficient (NRC)) of varius...

is there any book discussing goldstone mode? i am not very familiar with field theory. Could anyone suggest some books accessible to a non-field-theory theorist? i guess the acoustic phonon is a goldstone mode but the optical phonon is not. Since a goldstone mode is associated with a...

I want to be able to differentiate between longitudinal(P) and Shear(S) waves in solids. Using one Acoustic emission (AE) senor placed 2 to 20 cm form a AE source e.g. a stress induced crack or pencil lead test, how can one detect both the P and S waves and determine what part of the receive...

Homework Statement One organ pipe open on both ends and one organ pipe open at one end and closed at the other are tuned on the same fundamental tone with frequency f = 264 Hz. a)How long is each pipe? b) Determine the first three harmonics of each pipe. c) There is an organ pipe open at both...

I am currently trying to incorporate the sensing of tool wear as part of my research, which is an investigation into an experimental manufacturing process that is probably most similar to milling. I have already been making use of force data, but would like to utilize acoustic data as well...

Hi everybody, In chapter 10 of Kittel's "Introduction to Solid State Physics" it is said that the zeros of the dielectric functions determine the frequency of the longitudinal modes of oscillation, \epsilon(\omega_L) = 0, Eq. (17). Am I missing something or this is actually an "unproved claim"...

I would like to measure the relative amplitudes (energy levels) of several specific frequencies in a noise field. I thought of attaching capacitive microphones to tubes that would resonate at those frequencies. I've visited hundreds of web sites that invariably give equations for...

Hello! Sorry, I don't have much of a formal education, but am an amateur singer (female, age 66, tenor) who experienced a BIG surprise during one of our choral concerts a few weeks ago. While a fellow tenor was singing a solo (Gounod "Sanctus"), I heard distinct undertones (fourths). I was so...

Hi, I'm not sure if this is the correct forum, or even the correct website but you all seem to know what you're talking about! I make native american style flutes, and have recently become interested in the physics of sound and soundwaves, etc. I've done well in my research, but have come...

Are there certain materials that reflect acoustic waves diffusely? Would the material need to have large (visible) surface features to produce this kind of reflection or can the surface be smooth? Are there materials that reflect acoustic waves in accordance with Lambert's cosine law?

Defining the period measured by a moving observer relative to a stationary source as T=t(n)-t(n-1) where t(n) and t(n-1) represent the times when two successive wavecrests are received respectively, the theory of the Doppler Effect leads zero and negative periods in the case of sonic and...

Hi, I'm making an AUV and need to design my own acoustic modem. Now, after hours of research I found these PDFs (attached). In theory, can I remove the signal generator from XXXXPinger.pdf, add a DTMF encoder and then use a build the transducer as described in bender2.pdf to transmit the...

http://www.aip.org/pnu/2006/split/779-1.html Diagram: http://aip.org/png/2006/260.htm Paper: http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000096000021215504000001&idtype=cvips&gifs=yes

Where does the sound difference between acoustic and their electric counterparts come from, even when playing the same sustained note (i.e., same frequency)?

the problems is that: two loudspeakers, A and B, radiate sound uniformly in all directions in air at 20 degree C. The acoustic power output from A is 8x10^-4 W, and from B it is 6x10^-5 W. Both loudspeakers are vibrating in phase at a frequency of 172 Hz. a) Determine the difference in...

I need help with a question about acoustic resonance. Sound of wavelength 20cm is produced at one end of a 32 cm long tube. Is it possible for resonance to be produced?

Is it possible to correlate the atmospheric acoustic vs. ground seismic waveforms from a charge detonation? Are there any physicists on this forum that recognise the acoustic and seismic waveform signatures from a charge detonation? Acoustic, Seismic wave function equation: \psi (x,t) = A...

I'm looking for data on "acoustic noise" produced regularly by the earth, nothing man-made. In particular I'm looking for noise sources outside of the normal range of human hearing (20Hz-20kHz). Of course there are numerous terrestial noise sources, such as earthquake tremors, but those aren't...

Can someone point towards some useful information for me about the frequency dependence (over the audio frequency range) on acoustic mirrors, acoustic waveguides/horns and interfenece and diffraction effects please? Thanks

I'm working on a project that involves 'acoustic radiation pressure'.. This means that an acoustic wave can exert a net force on some object, along it's propagation-direction.. if the object was a plate, it would look somewhat like this: ...... | ----||--wave--> |->Force...

http://www.princeton.edu/~globsec/publications/pdf/9_3altmann.pdf