Acoustic Definition and 174 Threads

I am working on an animal vocalization study and I need a clarification about acoustic impedance. All of the sources I have gone to are a bit too technical for me, so if you would be so kind to answer my question I would be very grateful! My question is this: What happens to a sound in high...

Hi everybody, I am working with ultrasound-induced cavitation (i.e. what is used in ultrasonic water-bath cleaners) and I can't make my mind around the concept. I recon cavitation happens when the acoustic pressure (p) induced by the sound waves is greater than the hydraulic pressure of the...

I'd like to learn more about acoustic analysis of musical instruments, but I have no idea where to even start. I've taken some acoustics courses and some fluid dynamics courses as well as structural vibrations. What I'd like to do is model an instrument and then have a numerically predicted...

I am considering applying spray-on acoustic/popcorn ceilings to reduce the noise level in my house. I haven't found any data supporting that popcorn ceiling reduce noise level. I am looking for data, physics, experiments, and tools to help me figure this out. I asked this question at...

I came across an article in American Journal of Physics recently that describes how to build an acoustic radar by transmitting a carrier modulated with pseudo-noise code through a speaker and simultaneously receiving the reflection with a directional microphone. One then does some signal...

Homework Statement A material has 104 atoms in its primitive cell with a speed of sound of 1500 m/s. It is well above the debye temperature. From Cv=3kb per atom, we calculate the volumetric heat capacity of 1.4*10^6 J m^-3 K^-1. What fraction of he heat capacity is in the acoustic branches...

Can someone explain to me the following: I have been told that acoustic impedance is analagous to mechanical impedance. For mechanical impedance (Z), Z = force / velocity and for acoustic impedance (Z), Z = pressure / flow However, in the mechanical case, force refers only to...

Hi everyone; I'm in need of mathematic assistance. Background: I'm in the process of constructing a home theatre and I'm undertaking the building of a 12" high rear-seat riser that I will be filling with sound-absorbing material so that it can be used as a bass trap to reduce modal ringing in...

We know that air molecules are subjected to random motion in different directions. A sound wave is a push toward these molecules to make a wave front to make them expand or contract in groups so that we can hear a voice message in our ears. The question is that what happens when different...

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...

Hi everyone, I'm working a on a project involving acoustic levitation. Right now we're trying to finish up construction of the apparatus. In particular, the reflector plate is proving to be slightly difficult. The transducer we're use has a resonance frequency of about 29.95 kHz. As far I...

All, I'm doing an acoustics homework assignment and I'm having some issues. The velocity profile at time=0 is an N-shaped that goes from -1 to 1. I'm supposed to use the 1-D wave equation to find the "governing equation that describes the spatial/temporal air displacement of this wave"...

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...

Homework Statement Find the specific acoustic impedance for a standing wave p=Psin(kx)exp(jwt) where p is a complex variable.Homework Equations z = p/u (all variables are complex) u = (A/rho_sub_0*c)*exp^(wt-kx)The Attempt at a Solution Approaching this problem it seems that I have all of the...

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 I solved the helmholtz equation \Delta\Phi+k^2\Phi=0 to find the velocity potential in the cylindrical resonator. Since my answer is only a function of radius r and independent of time t, how can I find the acoustic pressure? what is the formula ? I know the formula p=-density*...

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. I'm trying to develop a clear image of Raman and Brillouin scattering in my head, but one uncertainty I have is what are the physical differences between the generation, propagation, and any other characteristics between Optical and Acoustic Phonons in silica fibre (such as, what is it...

Homework Statement In search for insects, a bat uses an echolocating system based on pulses of high frequency sound. These pulses are 2.0 ms in duration, have a frequency of 50 kHz, and have an intensity level of 100 dB at 1.0 m from the bat's mouth. Assume that the bat produces spherical...

1. Homework Statement Actually I am doing a research project about Noise Isolation. I took my college cafeteria as an example and I was provided with a Noise Simulation software( Soundplan). There I can work mainly with the SPL and the absortion coefficients. I found another software ( EASE)...

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...

Homework Statement Acoustic tile which is locally reacting, for a frequency of 400 Hz, it has a normal-incidence specific impedance of 1500+i3700 (Kg/m2s). A plane wave in Air of 400 Hz sound with a pressure level of 86 dB in the absence of reflection is incident on the tile at an Angle X. How...

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...

http://www.newscientist.com/article/dn17319-physicists-create-black-hole-for-sound.html" The team cooled 100,000 or so charged rubidium atoms to a few billionths of a degree above absolute zero and trapped them with a magnetic field. Using a laser, the researchers then created a well of...

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...