Questions tagged [acoustics]

Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. Applications of acoustics are for instance the audio and noise control industries.

Filter by
Sorted by
Tagged with
1
vote
2answers
43 views

Would two planes passing each other at 1/2 the speed of sound create a sonic boom?

Scenario: Two fighter jets at an airshow are flying towards each other at 1/2 the speed of sound. (Their paths are offset so they will not crash.) When the pass each other, will either pilot or a ...
2
votes
0answers
42 views

Relationship between resonance frequency of a cup and amount of water filled

For a science project I chose to investigate the relationship between the resonance frequency of cups and the amount of water filled in it. I filled the cup with 10 grams of water each time, and used ...
0
votes
0answers
12 views

Pressure dependency of the end node correction in a double-ended resonator

I have an acoustic resonator which is tube shaped and open on both sides. The open ends of the tube open into a buffer volume. In the picture below I visualized my assumption. Measuring the resonance ...
1
vote
4answers
69 views

Plucked string at $t=0$ and its Fourier decomposition

Decomposing a function into a Fourier series is possible for periodic functions. Fourier transform, on the other hand, is used for aperiodic functions. How can we use Fourier series to analyse the ...
0
votes
0answers
15 views

Air - rectangular membrane system vibration and natural frequency [closed]

I'm struggling with the following problem: The boundary conditions are $w(x,y) = 0$ around the edges. I am supposed to find the natural frequencies of the system as a whole, and find the solution ...
2
votes
2answers
44 views

Why is it easier to bend a note down on a brass instrument than it is to bend up?

When playing a brass instrument, on a given harmonic, you can bend the pitch above (to a higher pitch) and below (to a lower pitch) where it sounds the best (while staying on the same harmonic, with ...
1
vote
1answer
21 views

Speed of sound in air and Laplace's correction [closed]

Newton wrote the bulk modulus for speed of sound by writing the ideal gas law in differential form, and, laplace wrote another expression by taking writing the differential form of the adiabatic gas ...
2
votes
1answer
39 views

Why do standing waves filter out all other frequencies but its natural frequencies

I was wondering about how standing waves filter out all other frequencies. I read online that it's because the other frequencies destructively interfere with one another. However as hard as I try, I ...
0
votes
0answers
24 views

Loss in a lossless wave equation. Why?

I have simulated a plane wave in a Finite Element solver. Starting from the general acoustic wave equation $\partial u^2/ \partial t^2 = c^2 \nabla ^2 u$, the weak form is $a(u,v) = \int_{\Omega} (v ...
0
votes
2answers
21 views

Why does ultrasonic ranging only work with ultrasound?

I've read a lot about ultrasonic ranging (measuring distance with an ultrasonic sensor), but I haven't been able to determine why such methods only work in the ultrasonic range. Why not infrasonic? Or ...
2
votes
0answers
50 views

Is the squeal a manifestation of the Painleve Paradox?

When a DJ does a rewind (suddenly reverses the direction of the vinyl’s rotation under the needle), a sharp squeal is produced. This squeal is neither simply the music played backwards (as a film ...
0
votes
1answer
47 views

Aren't sounds made by sinusoidal plane vibrations sound-lasers or SASERs?

I read the first sound laser (or SASER) was made in 2010 here. But if we're talking about the state of the phonons emitted then we could say that any sound created by a planar vibration has a unique ...
0
votes
1answer
24 views

How does the sound of a tuning fork depend on the size of a tuning fork?

The pitch of a note is how high or low it sounds. The pitch of a note depends on the frequency, or the number of vibrations each second. If you listen to the notes produced by a loudspeaker connected ...
0
votes
0answers
22 views

Colinear acousto-optic interaction

I have a question about some colinear acousto-optics interaction. The problem is as follows: the situation is stated in Royer & Dieulesaint, Elastic Waves in Solids vol 2, just before Eq. 8.62, ...
1
vote
1answer
23 views

Adding sound powers together

I am a developer working on a software application which incorporates some basic acoustic simulations. I am trying to assist another developer in implementing equations provided to us by the team's ...
0
votes
1answer
26 views

How does sound get generated when you whistle?

how does sound get generated when you whistle? I.e. what creates the sound/vibrations when you whistle on your lips?
0
votes
0answers
14 views

Counting number of Antinodes for Modes in 2D

In 1D cases for standing waves, if we have the 3rd harmonic on a string of length L, then there are 3 antinodes and 2 nodes in between. This means, for each wavelength, we can establish a relationship ...
40
votes
4answers
4k views

Why do you have to blow sideways on a flute?

If you were to play a flute, you would want to blow sideways across it, kind of like a bottle, like in Fig 1. Why would this be better than blowing straight in to the hole, like in Fig 2? It seems ...
0
votes
1answer
13 views

Sonic Doppler shift from a distant source

Probably most of us have heard the pitch of an ambulance change as it’s passed us, but that’s from a nearby sound source. If a sound source is far away, does the Doppler shift change? I find it hard ...
0
votes
1answer
14 views

Amplified Sound in another room

I was sitting in my room with my door open, because I have a cooler in my room that has a lot of noise when turned on. I was watching a video on my phone, but because of the noise from the cooler, I ...
0
votes
1answer
24 views

What is the difference between elastic and acoustic waves?

On Wikipedia, it is written that acoustic waves are elastic waves. If they are the same then why do we have two different names? Can someone please explain the difference between these two types of ...
2
votes
2answers
44 views

Why did static electricity make a humming sound?

My son was generating a lot of electricity the other day by rubbing his socks against the trampoline. He could shock others (and himself) with the static. What surprised me was that when he was ...
0
votes
2answers
25 views

Parabolic speaker dish diameter

I am trying to design a parabolic speaker to allow an audio signal to be emitted in only a single direction. For a single acoustic tone with wavelength $w$, what should the diameter of the reflector ...
1
vote
1answer
48 views

Can we apply simple mechanics laws on sound waves

I made up a question to make you understand my doubt , see Assume that a car is travelling with speed v to a wall . When car is at distance x from wall it emits a sound signal . Find time after the ...
0
votes
2answers
24 views

How loud really are ultrasound transducers?

There are a plethora of mini ultrasound transducers available. Many of which have a Sound Level SPL > 110dB. This seems extremely "loud". If you were to listen to one of these transducers, would they ...
0
votes
2answers
28 views

Does resonance by sound waves, or by any other similar means, occur at the molecular level?

When the frequency of sound waves match the resonant frequency of a structure, like a building or a window, resonance occurs which is clearly visible. This frequency depends upon the material and it's ...
0
votes
0answers
19 views

Relation between intensity at a point from a line source of sound and distance from the point

I've read that the intensity of sound due to a line source at a distance r from the line source is inversely proportional to r. I really don't understand why does this proportionality differ with the ...
0
votes
0answers
15 views

How does the resonant frequency of a glass slab depend on its thickness

I am interested in finding out how does the thickness of a glass slab change the resonant frequency of it. Since i know that resonant frequency not only depends on the material but also on the ...
0
votes
1answer
35 views

Sound signals would reach the both cities at the same time

The speed of light is independent of the motion of source and it is always constant in vacuum. The earth goes around the sun at speed of 200 kilometers per second. One can ignore the rotational speed ...
0
votes
0answers
23 views

Displacement and Pressure Wave [duplicate]

In the relation between displacement and pressure wave in sound how can there be maximum pressure when there is zero displacement of a particle,doesn't the exact opposite happen in a compression wave ...
1
vote
0answers
64 views

What is the approximate air pressure in acoustic levitation caused by the sound pressure? [closed]

I'm wondering how the sound pressure in acoustic levitation affects the actual air pressure within the standing wave. I've read that several atmospheres of air pressure can be caused by ultrasonic ...
0
votes
2answers
39 views

How does sound imparts vibrations to molecules in solids

How does sound imparts vibrations to molecules in solids which are tightly bounded. I understand the molecular bounding is very strong that is why it is solid and tough. So how does mere a tap on a ...
2
votes
3answers
63 views

When a tuning fork is struck, how does the struck tine induce vibrations in the secondary tine?

Background I'm currently writing a book on music theory and I'd like to include some background information on the physics of sound waves. My example of choice is to explain compression and ...
1
vote
2answers
43 views

Neglecting the gravitational term in an equation of acoustic wave

It appears that one can derive a wave equation if the gravitational force is considered in its derivation by using $$\frac{\partial p_0}{\partial x} = -\rho_0 g.$$ Here, $\rho_0 = \rho(p_0)$ and $p_0 ...
6
votes
3answers
71 views

What happens when buoyant force causes movement to exceed sound speed?

I was wondering if it is possible for an object of a certain material to be put in a buoyant medium in such a way that the buoyant force (caused by the pressure difference “above” and “below” said ...
0
votes
1answer
46 views

Why does stepping on the floor produce sound?

I've been thinking about this question for some time now, and couldn't get to any conculsion. My understanding is the following: 1) when my feet and the floor are far apart (a few centimeters), they ...
2
votes
1answer
60 views

Why does a running fan produces some sound?

We see that a running fan produces some "humming" sound - "The sound of air". What kind of sound it is? Why does a running fan produce some sound?
-1
votes
1answer
44 views

Why does a running fan causes some soundproofing in the room?

I notice that when I switch on my fan inside my room, the room becomes soundproof to a great extent to the outside noises. The greater is the speed of the fan, the greater is the soundproofing. When ...
1
vote
1answer
21 views

Cylindrical spreading transmission loss (underwater acoustics)

In underwater acoustics, transmission/propagation loss can be calculated using a spherical spreading formula out to a certain distance which we can call the transition range, after which a cylindrical ...
1
vote
1answer
34 views

How full a recipient is by hearing its sound frequency

I have a closed how recipient with a cylinder form, something like this: I have noticed that when I am dropping water through the hole, the collision of the water and the bottom of the recipient ...
1
vote
1answer
19 views

Behavior of sound on interface of 2 media

We say that sound travels faster in steel than in air. Thus if we want to know whether a train is approaching us we can put our ear on the rail track as we would be able to hear that quickly. Now ...
0
votes
1answer
22 views

what will be more appropriate to consider sound wave as a pressure wave or displacement wave

I was reading waves from H.C. Verma in which it was written when two sound sources vibrate in unison then at mid point between the sources a pressure antinode is produced but a displacement node . ...
2
votes
1answer
32 views

Doubt on calculation of a “general expression” on the energy of a travelling wave in a column filled with gas

I) SOME FACTS When we study mechanical waves, we essentially have to deal with $dm$ mass increments; then we can "expand" they as: $$ dm = \rho(x,t)dV.\tag{1}$$ Also, I think that it's pretty ...
0
votes
2answers
59 views

Sound waves travel with electromagnetic waves? [closed]

Do sound waves travel along/with electromagnetism and static electricity from the sun?
4
votes
1answer
61 views

Why are there no even harmonics in a closed pipe?

I have seen a diagram on sites such as hyperphysics.com that show that there is a missing bit every time so that it makes every harmonic odd. I was hoping I could get a more intuitive explanation. We ...
2
votes
3answers
48 views

What causes volume of sound to decrease with distance?

I know about the inverse square law however I do not know why it actually decreases. Does it have to do with sound absorption, it runs out of energy so the vibrations lessen or as distance increases ...
1
vote
2answers
31 views

Speed of sound in ideal gases

The equation of state for an ideal gas is given by: $$p = \rho r T \tag{1}$$ In the other hand, the speed of sound is calculated by: $$c = \sqrt{{\partial p\over \partial \rho}}\tag{2}$$ Using (1) ...
1
vote
0answers
44 views

The relative velocity of sound waves in Doppler effect

Let speed of sound in the medium be $v$ when the source is at rest w.r.t the medium. In the case of the observer moving towards the stationary source with a velocity of $u_1$, the speed of sound ...
-2
votes
3answers
187 views

Has anyone tried to find the wavelength to the Corona virus cell? [closed]

I have seen websites and videos that show how cancer cells can be destroyed using sound resonance oscillation. So has anyone heard of anyone who is in the field of sound resonance trying to capture ...
0
votes
1answer
27 views

How to mimic the amplitude of an instrument's sound waves? [closed]

for a homework project, I'm meant to imitate the sound waves of an instrument. The sound wave is calculated with the following formula, A = amplitude * sin(2 * pi * frequency * t) with t being time. I'...

1
2 3 4 5
40