Acoustics Definition and 130 Threads

bapowell submitted a new PF Insights post A Poor Man's CMB Primer. Part 4: Cosmic Acoustics Continue reading the Original PF Insights Post.

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...

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...

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

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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?

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...

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?

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...

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...

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...

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...

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...

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...

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...

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...

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.

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...

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...

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...

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...

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...

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...

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...

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...

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

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...