What is Acoustics: Definition and 130 Discussions

Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics technology may be called an acoustical engineer. The application of acoustics is present in almost all aspects of modern society with the most obvious being the audio and noise control industries.
Hearing is one of the most crucial means of survival in the animal world and speech is one of the most distinctive characteristics of human development and culture. Accordingly, the science of acoustics spreads across many facets of human society—music, medicine, architecture, industrial production, warfare and more. Likewise, animal species such as songbirds and frogs use sound and hearing as a key element of mating rituals or marking territories. Art, craft, science and technology have provoked one another to advance the whole, as in many other fields of knowledge. Robert Bruce Lindsay's "Wheel of Acoustics" is a well accepted overview of the various fields in acoustics.

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  1. G

    I What are the properties of a Sound Pressure Wave going down into a Cone?

    I do not remember the correct terms to look this information up on Google. I once read that as a pressure wave goes down into a closed cone every time cross sectional smaller by 1/2 the pressure wave doubles. My cone is 12" x 12" on the open end and 1"x1" on the closed end. Cone is 24" long...
  2. S P

    B What sound frequencies can pass through a hole in a wall?

    Hello, First of all, I will try to overcome language barrier as this is not my native language and the more topic is scientific - the more chance for me to get lost in translation. Apologies for poor grammar in advance. I marked it as Advanced post, so apologies if this has to be corrected by...
  3. Daniel Petka

    I Why singing a note while playing a note creates a difference frequency

    If you play a note of a certain frequency on a flute and simultaneously sing a note at a different frequency, then you create a third frequency that wouldn't be there if you play or sing in isolation - and the frequency of this subharmonic is the difference of the flute frequency and the voice...
  4. C

    I Understanding Ultrasound Attenuation and Reflection in Aluminum Sheets

    Hello. I write this in regards to enquiring whether you can address various questions I have in relation to acoustics and the physics of sound. In particular, I am interested in ultrasound. I have various questions in relation to it. In particular, I am interested in understanding the nature...
  5. T

    How to Implement Beamforming in Ultrasound Diffraction Tomography

    I'm currently working on an ultrasound diffraction tomography algorithm that incorporates a BentRay based Time of Flight approach. In the experimental setup, a circular transducer array is deployed around the region of interest, with each sensor actuated sequentially to collect acoustic...
  6. coby_rumblewood

    Acoustics Intuition of Subwoofer Mounting

    I have an acoustics question regarding mounting of a subwoofer enclosure, here is wireframe view of situation: I have a sealed subwoofer box lets assume it is running high power 250 W RMS. It has flanges that come out that have 30 Duro Isolating Pads between the flanges and the base board...
  7. hagopbul

    About the news of missing Titan sub

    TL;DR Summary: Heard in the news about using sonar to locate the sub Hello : After the sinking of the ship near the Greek shores , carrying of alot of people , there was another accident that include 5 tourists and a submarine visiting the titanic , which went missing Some technical notes...
  8. Intel Xeon

    Acoustics Question Confusion (Test Q)

    This Problem is from a test that has already been attempted. This problem required some amount of imagination so many of my peers came up with their own unique answers. It would be very helpful to get to know what the actual solution is. Any amount of assistance will also be helpful. Question...
  9. Aethermimicus

    I What is the function of the air cavity inside drums?

    I'm trying to understand the function of the air cavity inside drums. I've read that 'The air cavity inside the drum will have a set of resonance frequencies determined by its shape and size. This will emphasize some frequencies at the expense of others.' Then what are the resonance...
  10. mohamed_a

    I Acoustic wave properties and momentum

    I have read about doppler effect in acoustics so i searched for the relation ship between wavelength of wave produced by linear movement of body and its momentum along with other dependent variables such as density of fluid (leaving acoustics for a second) and temperature but souldn't find a...
  11. Anachronist

    I Humming Top Acoustics: Unearthing the Mystery

    I remember having a humming top toy when I was a small boy, and I vaguely remember it made a sound when spun. Here's a 30-second example: ...and more examples are available on YouTube. It's interesting to me that the sound doesn't start right away after the driving force is removed. It builds...
  12. Huzaifa

    I Time period of Beat (acoustics)

    $$y=2 A \cos 2 \pi\left(\frac{\nu_{1}-\nu_{2}}{2}\right) t \sin 2 \pi\left(\frac{\nu_{1}+\nu_{2}}{2}\right) t$$ Can you explain me the significance of the above equation in the context of waves and oscillations? It's something to do with 'beats,'.
  13. A

    B Simple Acoustics Question -- Which neighbor hears the other better?

    There are two blocks of apartments separated by a narrow alleyway. Person 1 is in the middle of the room in Apartment 1 (first floor if you are in the UK and second floor if you are in the USA!) and Person 2 is on the ground outdoors in the alleyway. If both people speak at the same volume...
  14. Tech_Rizzle

    I Amount of Noise extinction in Acrylic glass per thickness in mm

    Hey guys, I need your help with the following topic on which I couldn't find sufficient information on the internet to solve. In the need to further insulate my velux roof swing window against against airborne motor and tire sound from the nearby street, I came across the idea to install an...
  15. R

    What is the Relationship Between Music Composition and Biological Processes?

    Mostly I'm a composer of electroacoustic music (PhD, studio composition) so my 'expertise' in physics would likely be corralled by acoustics or possibly psychoacoustics. I do have an interest in biology and I have an undergraduate degree in Psychology (the department was mostly behavioural...
  16. F

    How does a Western free reed work? (musical instruments)

    In this post, I will describe, as best I have been able to determine, how a Western free reed works. As it is unlikely I will run into a physicist here who specializes in reeds, I will just ask people to speculate on the behavior of a reed given what you know about fluid dynamics or the...
  17. BillTre

    Music Stonehenge Had Good Acoustics For Voice And Music

    Tests of a mini-Stonehenge indicates it was acoustically suited for music and voices. Science News article Original research article Thus is was probably a good place to use for meetings of humans involving different audio features. This argument is reminiscent (to me anyway) of a David Byrne...
  18. jeremiahrose99

    I Solution to the 1D wave equation for a finite length plane wave tube

    Hi there! This is my first post here - glad to be involved with what seems like a great community! I'm trying to understand the acoustics of a finite plane-wave tube terminated by arbitrary impedances at both ends. So far all of the treatments I've managed seem only to address a different...
  19. N

    I Cavity resonances between two long parallel plates

    Consider two rigid and infinitely long parallel plates (say they are of infinite length in X direction, so running from -inf to +inf in X axis) separated by a distance d (say measured in Y-direction). Let the space between the plates be filled up with a fluid that supports acoustic waves. If we...
  20. C

    Acoustics type question on reflection....

    Hi, hopefully someone can help with showing me how I can work this one out as I am new to the topic area and a bit stumped. A piece of machinery is emitting a sound power level of 100 dB at 40 kHz. Calculate the level of the return signal after reflection from a wall 5 m away using the...
  21. K

    Best Resources to start with for waves and acoustics

    Hi All, i have been mostly into the structural analysis domain ...now want to explore the world of sound waves/Acoustics. What should be the best way to start with? Regards Kapil
  22. Cathr

    Accoustic waves notions (propagation in a tube)

    Please help me with this problem I am facing, I am lacking notions of acoustics and I would be very grateful if someone could clarify them: A tube has a revolution symmetry arounf the ##x## axis and has a section dependent of the value of the abscissa (x), so the profile ##S(x)## is known. The...
  23. The Bill

    I Microphones at longer wavelengths than their size?

    Why are microphones pretty good at picking up sound that is much longer in wavelength than the size of the microphone? 1khz sound has a wavelength of around a third of a meter, varying a bit depending on atmospheric conditions. Yet a 1cm diameter electret microphone can pick it up reasonably...
  24. E

    Phase relation between strain and particle velocity

    I'm trying to understand the following derivation. Starting with the one-dimensional equation for a traveling wave ##u = u_0 \exp{[j(\omega t - \beta z)]}## the goal is to derive the phase relation between strain and velocity. The author first derives the relationship between strain and particle...
  25. S

    Question about acoustics -- Wine glasses filled with varying amounts of water

    Here’s my experiment: I have a wine glass half full of water. I tap the edge with a metallic object to make a ringing sound. I recently bought a nice microphone and some acoustic software (Spectrum Analyzer Pro Live) and I’m trying to analyze the resulting sound to determine the resonance...
  26. I

    Angular frequency of a non-sinusoidal pulse

    Hey all, so I’ve been learning nonlinear acoustics and have encountered a conceptual hurdle in my studies. When using a model, such as a form of the classical Burgers equation, to propagate sound waves, you generally have a “characteristic angular frequency” in the equation (often represented by...
  27. C

    Underwater acoustics: transmission loss at long distance

    Hi all, I have some problems to understand how to calculate the transmission loss at long distance, which model do I have to use? I was looking into the energy flux model (Weston model), but I didn't understand at what range I should switch from "mode stripping" to "single mode". I am working...
  28. Sophrosyne

    B How does the ear distinguish multiple different pitches?

    A chord played on a piano is multiple different pitches, each at a different frequency, played simultaneously. The ear hears this as separate sounds. The cochlea of the ear is organized by tone (tonographic organization), from highest to lowest frequency. So a triad chord will stimulate three...
  29. E

    I Helmholtz resonator with multiple necks--formula?

    Does anybody happen to know the formula for resonant frequency of a Helmholtz resonator having N necks? Physics is not my field and I'm a bit over my head. I need the formula for a computer program related to musical instruments--this is the only thing holding me up. It seems like it would...
  30. F

    Acoustics (Environmental Noise): LAFmax vs Shot Noise Level?

    Hello, new poster, I am trying to do a fairly simple, but non-standard, environmental noise model run for a shooting range. The standard against which noise from the shooting range is to be compared is the Shot Noise Level (SNL). SNL is defined as the logarithmic average of the 25 highest...
  31. Rorshach

    Classical Acoustics Handbook: Malcolm J. Crocker vs Everest & Pohlmann

    Hello! I am looking for a good handbook in the acoustics field. I read that handbook of acoustics by Malcolm J. Crocker is one of the best, second one that came up in my research is master handbook of acoustics by Everest & Pohlmann. Can anyone recommend one over the other, or maybe knows...
  32. R

    Applied Acoustics - decouple a speaker and a wooden table

    If several sheets made of some kind of rubber are being used as acoustic insulators, which configuration would be more efficient to decouple a speaker and a wooden table, absorbing most vibrations? (Ps: Image not drawn to scale)
  33. Rorshach

    Tympani in a concert hall: calculating Sound Pressure Level (SPL) and delay

    Homework Statement Hello. I have a problem, which is as follows: A seat in a concert hall is 84 ft from the tympani. The tympanist strikesa single note. The sound pressure level of the direct sound of the note at the seat is measured to be 55 dB. The first reflection from the nearest sidewall...
  34. D

    A Helmholtz Resonator: attenuation vs. amplification

    Hello guys, I read the other threads about HR, resonances and so on, but I couldn't find a clear explanation of what the practical implications of using a HR are. From one side, HR is described as a "reactive element", used in several contexts to attenuate a specific noise by means of...
  35. N

    About acoustics physics -- The Wave Equation and diminishing sound intensity

    Hello everyone! :-) Actually I'm starting to understand acoustics physics and I figured actually out about this equation: $$\frac{\partial^2\psi}{\partial t^2}=c^2 \nabla^2 \psi$$ which describes practically about pressure and propagation speed into space and time. I know also this equation...
  36. D

    Introductory Acoustics Homework Help

    Homework Statement Hi there, I am a beginner in acoustics and there are severals problems I am currently struggling while I was reading the first chapter of "Theory of Vortex Sound" (available on Google books). Homework Equations For Q4[/B]: The Attempt at a Solution For Q2 and 3, as...
  37. M

    I Effects of Ultrasonic Transducer in contact with glass

    I'm looking for a way of using ultrasonic cleaning to clean the inside of a glass vessel filled with some sort of fluid by transmitting ultrasounds through the glass, rather than submerging the entire glass vessel. If an ultrasonic transducer, let's say something with a maximum frequency of 40...
  38. D

    How Does the Mean Free Path Affect Acoustic Wave Continuity?

    Hello everyone, I have a question regarding the implication of mean free path and pressure acoustics. I have seen several publications on the internet and also calculated the minimum displacement of a wave in air using the formula dp=v * rho * *2*pi*freq. * dx The values of displacement can...
  39. J

    A Calculate Third Octave Band Response from Narrowband Data

    I have a signal that I am able to calculate through an acoustic model for airfoil noise. I am told that the model solves for a narrowband frequency response, however, my measurement data is provided in third-octave band representation. How do I convert my current dataset to the third octave...
  40. T

    B Why does end correction in pipes change with radius

    This being WRT resonating pipes. Apparently the acoustical length of the pipe is different to the physical length due to the vibration of the sound particles moving the particles at the opening so that the physical length is no longer the length of resonance. I've found many sources on the...
  41. F

    Acoustics & Physics: Is Frequency Linked to Wave Width?

    Is it true that the higher the frequency of sound, the narrower the wave will be?
  42. Alfreds9

    Finding the acoustic point in a valley

    Hello, I have a practical problem, I'd like to find the "best" spot to hear sounds in a valley (forgive me if "acoustic point" isn't an appropriate term, I just couldn't come up with anything better and scrolling an acoustics text didn't help), or at least a non-blind spot (one which instead...
  43. S

    Acoustics and Fluid Flow - COMSOL 4.2

    Hello everyone, First of all I am new here~ Second, I would like to "prove" on COMSOL that soundwaves (sound vibration) can alter/reshape the fluid flow Can someone tell me the physics i should use as well as all the other parameters to make it work? if someone is more experience can they...
  44. louisnach

    Exercise involving acoustics physics engineering

    Homework Statement A disturbance signal propagates in a ventilation duct with cross-sectional area A=0,04m2. The fundamental frequency of the disturbance signal is 250Hz and its spectrum consists of odd harmonics only. Choose the appropriate filter options for rejecting this particular...
  45. C

    Let's talk NVH/Exhaust acoustics tuning

    To start let's make a goal. The goal is to figure out what causes the difference in sound to the Maserati Granturismo motor a 4.2 cross plane v8 with a higher pitched and more growl exhaust note... vs ... The base C7 corvette v8 which is a 6.2 cross plane v8 which is has a harsh thumper...
  46. T

    How Do Bessel Functions Predict Sideband Amplitudes in FM Modulation?

    Homework Statement For the FM modulation, the amplitudes of the side bands can be predicted from v(t)=ΣAJn(I)sin(ωt) Where is a sideband frequency and Jn(I) is the Bessel function of the first kind and the nth order evaluated at the modulation index .Given the table of Bessel functions...
  47. Z

    Displacement and Pressure in acoustics

    So my question deals with open-open tubes. When there is a displacement antinode there is a pressure node. I can somewhat conceptualize this because of the boundary condition where the pressure at the ends needs to be atmospheric. But I am confused about the ideal gas laws relation to this...
  48. Phil Freihofner

    What are the physics of acoustics and how do they apply to music and the oboe?

    Hi - My name is Phil Freihofner. I live in Albany, CA. I am an alumni of UC Berkeley with an AB in Music. My main interests (pertaining to this site) involve the physics of acoustics, especially as they apply to music in general and the oboe in particular. I am also a Java programmer and am...
  49. D

    Amplitude and Energy: A Simple Explanation

    I tried to come up with a simple calculus-free explanation for why the energy in a sound wave is proportional to the square of the wave's amplitude for my musical acoustics class. I think this makes sense, and seems to just be an elaboration of what Donald Hall writes, but I haven't seen it...
  50. H

    Elementary Acoustics Homework: Deducing End Correction

    Homework Statement ; I plotted a graph of length against 1/frequency,determined the slope,which was the speed of sound. I got stucked in the (b) part,when asked to deduce the end correction from the graph drawn.[/B]Homework EquationsThe Attempt at a Solution ; I attempted using the formula end...
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