What is Acoustics: Definition and 129 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. D

    Explaining the Sine Formula to Acoustics Students

    I'm (a music academic) teaching a musical acoustics course to a very mixed group (music students, science students, and neither). Today, I covered the basic concept of simple harmonic motion and how this produces a sine wave pattern of motion over time. In the extra time we had left over, I...
  2. T

    Optimizing sound energy transfer through plastic medium

    Hi everyone, I am looking to improve the transmission of sound from a small 1/2" electro-mechanical transducer through a plastic medium (about 1/4" thick). I understand plastic is not a great medium for this but I do not have the ability to change this. The defacto setup doesn't work too...
  3. andrewkirk

    Acoustic 'beats' from mismatched musical frequencies - Comments

    andrewkirk submitted a new PF Insights post Acoustic 'beats' from mismatched musical frequencies Continue reading the Original PF Insights Post.
  4. D

    Why do sound waves with slightly different frequencies create beats?

    I have a question about 'beats' between two sound waves of slightly different frequencies. Basically, I think I understand everything on this page (and have read a few textbooks on this): http://www.animations.physics.unsw.edu.au/jw/beats.htm . And in practice, I work with this concept all the...
  5. S

    Resonant frequency in acoustics

    Hi, A question popped into my mind which I've never thought of in 20 years of making music: when you hold a tuning fork against a simple resonator (a guitar body, a table, any object with some volume really), the resonator amplifies the tuning fork's sound and you hear the tuning pitch louder...
  6. NPB777

    Ultrasound Transducers and Simulator

    Presently I am working on Underwater Acoustic Wireless Transmission. I desire to measure water parameters at the bottom of the surface of the water and then pass it to the water surface using Ultrasound. There will be a buoy at the surface which is half submerged and half floating. The floating...
  7. NPB777

    Variation of Frequency of sound underwater

    Hello, I am very much interested to how frequency of sound varies in water. Also, how the frequency varies with temperature and depth? What are the different formulas related to this? Secondly, how can we determine the best frequency of operation? I would be very thankful if anyone could answer...
  8. Z

    Acoustics vs. Optics/Photonics career prospects

    I'm currently an undergraduate Engineering Physics student. My university offers the following specializations within the program: - Renewable Energy - Biomedical Physics and Acoustics - Optics/Photonics I know this mainly comes down to personal interest, but I'm also interested in the...
  9. E

    Why is dispersion important in wave propagation?

    In the propagation of non-monochromatic waves, the group velocity is defined as v_g = \displaystyle \frac{d \omega}{d k} It seems here that \omega is considered a function of k and not viceversa. But in the presence of a signal source, like an antenna in the case of electro-magnetic wave or a...
  10. the potato one

    Programs Graduate Degrees in Acoustics?

    If anyone has anything to say at all about acoustics, I'd love to hear it. I'm finishing up a B.A. in physics this year, and I would like to pursue a Ph.D. in acoustics, architectural acoustics, acoustic engineering, something like that. I've also seen degrees in mechanical engineering with a...
  11. P

    Acoustic horns and impedance matching

    I found a fast solenoid valve lying around (~1ms rise time) so I thought it would be fun to hook up to a compressed air line and use to generate some really loud bass. I hooked it up to a function generator and air supply only to find that it was disappointingly quiet (well not quiet, but...
  12. K

    Sound standing waves paradox....

    If you seal a loudspeaker at the end of a tube and close the other end of the tube you will get standing waves; but what are the boundary conditions at the speaker for the sound pressure wave? Pressure =0 or Pressure = MAX? I find no mention of this in the literature. To find out I performed a...
  13. Y

    Classical Acoustics Music Physics Maths: Get the Book You Need

    For college we have to write a 3000 word essay on a subject so an idea I had was to firstly explain the maths/physics behind music and then break up a piece of classical music into its sine waves. However, my acoustics knowledge is limited. Does anyone know of a good book/books that explain...
  14. J

    Cosmic acoustics -- why no intermediate waves on CMB map

    I fully understand the representation of the set of waves that are either at full compression or full rarefaction at recombination, thus, yielding a CMB map. But at this time are there no waves that are intermediate, e.g. 50% of the way to full compression or full rarefaction. Why don't these...
  15. spareine

    Why can't pinging excite singing overtones?

    I recorded the sound spectra of a singing wineglass (rubbed the rim with a wet finger) and a pinging wineglass (tapped anywhere at its wall) with a smartphone. Evidently the fundamental tones of both vibrations are identical, but the overtones are very different (harmonic vs. anharmonic). As the...
  16. E

    Odd (pretty) waveform for third harmonic of violin E-string

    I lightly placed my finger a quarter of the length down the E-string of a violin and drew the bow, forcing the third harmonic. I used an oscilloscope app to look at the waveform. I got this unusually regular pure pattern...
  17. Kyle Burris

    Mechanical noise - A/C and radon fan standing wave hum

    Hello, I am moving into a new house, remodeling, etc. & am installing a new A/C compressor and radon fan. Being that low frequency noise highly bothers me & affects my insomnia quite a bit, I am trying to look at all considerations regarding acoustics, mechanical sound propagation properties...
  18. M

    Absorptive type sound insulation

    Could you tell me the physical reason, why the absorptive type sound insulation (Windowpane with some thickness) is effective only at high frequencies of sound source?
  19. Vir27

    Low tech telecommunications (sound)

    I'm a historian. I've struck on a curiosity about telecommunication technology in pre-modern times. I've read about a number of methods, and I'd like to ask some physics questions that got beyond my ken. This information is for my curiosity and creativity, not for any rigorous study, so I may be...
  20. Saumya Kar

    Difference between acoustic pressure and fluid pressure

    While the sound waves travel in a medium, let's say a fluid, what is the difference between fluid pressure and acoustic pressure ? Are these entities same?
  21. A

    Physics investigation guidance: Vibration of circular plate

    Hi, I have previously made a post in order to gain some insight in my rather out of control project. Long story short I am investigating vibration of a circular plate and its standing waves. After consultation at this forum I have been guided in the direction of acoustics and bessel functions...
  22. H

    Planar wave expansion cancelling through interference

    Hello everyone! In a hypothetical 3D space, with no boundaries around, homogeneous normal conditions, what would happen to the advancement of a planar wave front produced at t=0 with 2cycles in length, λ=3.5m, moving with vector speed "c-arrow=1i-arrow" if an identical planar wave of 2cycles in...
  23. R

    Ultrasound absorption by particles in water

    Hi All, I am in need to calculate the ultrasound (20MHz) absorption of particles (polystyrene of size 15 microns) in water. I tried to search in the internet, but couldn't find any simple analytical expressions. Can someone please help me ! Thanks in advance! Regards, Radel...
  24. V

    Damped Driven Harmonic Oscillator.

    Homework Statement An oscillator with mass 0.5 kg, stiffness 100 N/m, and mechanical resistance 1.4 kg/s is driven by a sinusoidal force of amplitude 2 N. Plot the speed amplitude and the phase angle between the displacement and speed as a function of the driving frequency and find the...
  25. X

    FDTD of (ultrasound) wave propagation through muscle

    Im a mechanical engineering student currently, with a third year project of simulating ultrasound propagation through the abdomen. Currently i just want to simulate it going through muscle with no obstacles. I don't really understand where to start, I have formed some equations based on the wave...
  26. S

    Continuity of velocity at the interface

    Dear experts, While solving the wave transmission at an interface for an acoustic wave problem, a boundary condition states that the "velocity of a fluid particle at the surface must be continuous". Could you please let me know why is it required, and a physical insight of what would happen if...
  27. N

    Acoustics + Optics + Oceanography ?

    Hi Everyone, I am about to finish my PhD in underwater acoustics. I am thinking of postdoc positions and research areas which might cover: oceanography and optics with acoustics. I still have to learn a lot before generating any ideas on my individual research career. But was wondering if...
  28. D

    M.S. Mechanical Engineering in Mechanics vs Robotics/Controls

    Hello fellow PF members, I'm currently in my senior year in Mechanical Engineering at Oregon State University. I'm considering going on to get my Master's Degree to gain more knowledge (since I'm fascinating by them). I really like Math and have a Math Minor already. I am looking to go into a...
  29. SalfordPhysics

    Helmholtz Resonator using voltmeter

    Hi, I am trying to understand how precisely a voltmeter is used to measure the resonant frequency of a sound wave in a helmholtz resonator. Is it simply that the maximum voltage corresponds to the resonant frequency? A detailed description or external link would be great. Many thanks.
  30. G

    Schools Exploring Acoustics & Computer Engineering: A New Path?

    Hello everyone, well this is my first post and i hope someone could help me I'm starting choosing what to study now and at first i choose Aerospace Engineering, but now I'm towards to Computer Engineering. Also I'm really interested on audio and acoustics. I saw an university that have Acoustics...
  31. bartekac

    Acoustic waves - factors determining their form

    Hi, I am not a native English Speaker, so some words might not be appropriately used below, but I will try my best to explain what I was thinking about. In general, I have never learned how acoustic waves emerge microscopically. The application of the theoretical knowledge I acquired was always...
  32. Y

    Exhaust Acoustics for Subaru WRX 2.0L Turbocharged Engine

    Hello, I am working on a custom car project, and will be using a Subaru WRX 2.0 liter turbo charged engine. I did a search under the question I am looking for an answer to, but only found one thread that was closed. I hope you all might be able to educate me, on what my possible options are. I...
  33. E

    Home Theater Acoustics: Subwoofer Placement

    Hi all, I'd like some advice on subwoofer placement for new home theater. It is a downward firing sub, with the port also being downward and has plastic/rubber feet. It is currently placed on carpet, which is over wooden floorboards as it's on the second floor. I'm trying to minimise the...
  34. R

    Ideas for an Acoustics Project?

    Does anybody have any ideas for a neat acoustics project for an advanced undergraduate acoustics course? I'd like to do something that actually accomplishes something worthwhile. Are there any current efforts in acoustics to which I might contribute or problems I might solve that would have some...
  35. H_man

    In acoustics is there something analogous to skin depth in EM?

    Hi all The reflection and transmission of a pressure wave at a boundary depends on the relative impedance of the two media. I'm pretty new to acoustics but the textbook I've been looking at doesn't seem to specify that the such calculations are only valid when the medium is at least a few...
  36. M

    RMS of complex waveform (acoustics)

    Hey everyone, just got a quick question in acoustics. I am mainly looking for a mathematical understanding Homework Statement Consider two harmonic plane progressive waves of the form \tilde{P(x)} = \tilde{A}e-jkx and\tilde{P(x)} = \tilde{B}e+jkx traveling in opposite directions. Showing...
  37. S

    Learning Materials for Speech, Music, and Acoustics Research

    I am interested in starting to research into the acoustics of speech and music. In particular I want to analyze the spectral profile of human voice in hopes of finding relationships between it and music. A possible future direction for this research is to improve synthetic speech to mimic...
  38. T

    Can color of the room change the acoustics?

    I know it's probably a silly question, but does it?
  39. A

    Acoustics: Directing Sound Waves

    Hey, I'm just curious if anyone has designed a device that can direct and concentrate sound waves like a parabolic mirror? Since both sound and light are waves, I assume there must be a shape that allows one to "target sound" much like using a magnifying glass to focus light. On a related...
  40. M

    Acoustics essay - help? [IB]

    Does anyone here know of some interesting problems in acoustics? I'm writing an extended essay for the IB Diploma (I'm sure you've been annoyed by a few others asking similar questions) and am at a bit of a loss right now. The topics I've looked at so far have either been overresearched to the...
  41. M

    Physics with Application; Acoustics; Trumpet

    From Acoustics, Resonance, Energy, Power, Intensity and The Doppler Effect Homework Statement An old-fashioned hearing trumpet has the shape of a flared funnel, with a diameter of 8 cm at its wide end and a diameter of 0.7 cm at its narrow end. Suppose that all of the sound energy that...
  42. P

    Research combining physics with sound, acoustics, music

    Hello! I am a recent university grad, majored in physics, with a strong background in programming and maths. I've had a couple non-physics research positions, and am looking to go back to school for a masters. All my life I've been very passionate about music, from composing classical...
  43. S

    Acoustics of Space? Exploring Communication with Other Civilizations

    The other night I was laying in bed thinking about how we might contact another civilization or at least listen in on one. I then began thinking about the acoustics of space- which I know nothing about. I went to school for audio production so am familiar with acoustics in general but am curious...
  44. N

    Active sonar and submarines, acoustics

    Hi, a newb-question here. How does it work? Let's say an active sonar from a ship sends out a sound-wave at the suspected location of a submarine. How does it actually detect the submarine? I mean, why is the echo the active sonar receives back so special? I mean, if the sound wave hits...
  45. P

    Stethoscope Acoustics: Explaining Low/High Frequency Filtering

    Hi, everybody. I run a blog about my training as a physician assistant, and I'm planning a video that discusses just how stethoscopes work. I understand the general principle, but I'm having trouble with the WHY for two of the facts I intend to share: 1) Stethoscope diaphragms filter out...
  46. S

    Acoustics and Frequency Question (easy)

    1. Two nearly identical forks one of which has a frequency of 384Hz produce 7 beats per second when they vibrate at the same time. A small clamp is placed on the 384Hz fork and then only 5 beats per second are heard. What is the frequency of the other fork? Homework Equations I...
  47. R

    Acoustics - Critical Bandwidths ?

    Hello! I'm getting a bit confused with how to deal with sound waves that are within one critical bandwidth of each other. I do not fully understand how you are meant to combine the intensities of sound waves when they lie within one critical bandwidth?! I would really appreciate some...
  48. R

    Understanding the Applicability of the Acoustics Wave Equation

    Hello! When considering the acoustics wave equation \frac{\partial^{2}P}{\partial t^{2}} = c^{2} \nabla^{2} P I don't really understand why you can say that the applicability of this equation varies for different sound pressure levels. I don't see why this shouldn't hold for all...
  49. F

    Automotive Acoustics engineering: Automotive exhaust harmonics

    I thought I would try to discuss this here since there seems to be a large misunderstanding in automotive forums and I want to learn the reality, not someone's theory. basically, I have a car here in which we removed one of the many mufflers. Piping is constructed as 2-1-2. It converges to...
  50. T

    Acoustics in conical volume

    Homework Statement This is a problem I've been pondering, and I simply need some recommendations for texts to read on the topic. Suppose you have an enclosed air chamber with an acoustic source on one end (http://beckerexhibits.wustl.edu/did/images1/hatpatent.jpg" ). How can one predict...
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