Skip to main content

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
0 answers
29 views

Acoustic Field Theory examples and resources

Does anyone know of any good resources to study Acoustic Field Theory? Mainly focused on reflection and refraction of acoustic waves. I currently have online versions of B.A. Auld's book on Acoustic ...
1 vote
1 answer
36 views

Local Maxima in a Dispersion Curve

Hello I programmed a dispersion curve and plotted the phase velocity. I am noticing that for one of my modes (the S2 mode) my phase velocity reaches a maxima and then decreases. Is this a physical ...
iato's user avatar
  • 145
0 votes
2 answers
31 views

Understanding particle velocity and wave velocity [closed]

If particle velocity is less than wave velocity how can particle disturbance reach A to B faster than particle velocity
Arjun Raj's user avatar
  • 117
0 votes
1 answer
41 views

Sound Timing: Stationary vs. Moving Source - Who Wins?

Case - 1: A stationary source emits sound and an observer stationary is at 'd' distance apart. Case - 2: A moving source emits sound when an stationary observer is at 'd' distance apart. Will in both ...
Sam Tunkaho's user avatar
12 votes
8 answers
5k views

Feynman claimed "The ear is not very sensitive to the relative phases of the harmonics." Is that true?

In The Feynman Lectures on Physics, Dr. Richard Feynman claimed that the ear (I assume he meant the human ear) is not sensitive to the relative phases of harmonics. However, I was asked to test ...
Dan Bullard's user avatar
0 votes
0 answers
19 views

Temporal absorption coefficient from complex wavenumber

A complex wavenumber $k=\beta-i\alpha$ can be defined, that when substituted into a time-harmonic solution $e^{i(\omega t - kx)}$ yields $$e^{-\alpha x}e^{i(\omega t - \beta x)}$$ The first negative ...
korokame's user avatar
1 vote
3 answers
60 views

Is sound louder in a solid compared to air?

Consider this experiment, where it is shown that the sound of the metronome is louder when you hold the acoustic sensor directly towards the table. Many explanations in the internet argue that it is ...
Blue2001's user avatar
  • 298
1 vote
2 answers
36 views

Question about waves in a fixed string

consider a string that is fixed at both ends. This string is connected to a metal stick. When I hit the metal stick, sound waves (longitudinal and transversal ?) will propagate trough the metal and ...
Blue2001's user avatar
  • 298
0 votes
1 answer
21 views

Amplitude based on number of equal sources

A homework problem states the following: In a urban road with a lot of traffic the sound level produced by a flow of a 100 cars per minute during the day is $B_1 = 80$ dB. Calculate the sound level $...
NICOLA TROMBINI's user avatar
0 votes
1 answer
72 views

Can absolute silence exist and how are thermal and quantum noise a limit? [closed]

For my exam, I must answer the question: can absolute silence exist? While doing research, I obviously heard about noises internal to our body and noises external to our environment but I also heard ...
Leane Meireles's user avatar
1 vote
1 answer
33 views

Can active sonar detect objects by "fluorescence" in a different frequency from the original pulse?

Just now a bumblebee flew past me (more than a meter away), and for a moment its prominent droning sound seemed to make a vibration on my face I could feel. It made me wonder: consider a bumblebee, ...
Mike Serfas's user avatar
0 votes
1 answer
32 views

Changing the frequency of the tuning forks

I just bought some tuning forks with frequencies of 128 Hz and 512 Hz. However, when I tested them using an app, their frequencies turned out to be lower than the specified values. How can I increase ...
zarvis12's user avatar
0 votes
1 answer
42 views

How does flute work?

I started learning flute a few months ago. Here in India you can buy two types of flute hindustani and carnatic. Hindustani flute has a simple acoustics. Lenth is inversely proportional to frequency. ...
Newtron Malayalam's user avatar
6 votes
3 answers
987 views

How does a guitar string produce sound?

I'm curious about the mechanism of a guitar producing sound. Of course, I know once a string is plucked it vibrates in a superposition of several harmonics, but what I don't know is what happens next. ...
Lagrangiano's user avatar
  • 1,541
0 votes
1 answer
33 views

Why is Acoustic Impedance Proportional to the Speed of Sound if It Measures Difficulty of Wave Propagation?

I am studying Advanced Level Physics and I am confused about the following entry in my notes: If acoustic impedance is a "measure of how difficult it is for an acoustic wave to travel through ...
Oliver's user avatar
  • 21
0 votes
0 answers
34 views

Conceptual doubts about Chladni Plates

For a divulgative project that I'm working on, we've built a two Chladni Plates a square and a circular one. The idea is to do a demonstration in front of high schoolers, accompanied by an explanation ...
Marcel DC's user avatar
0 votes
1 answer
63 views

Is there any deeper explanation behind this simple acoustic experiment?

my question is a bit inconvenient but let me explain: I recently saw an experiment for primary school where two strings are attended to a coat hanger (see here: https://www.youtube.com/watch?v=...
Blue2001's user avatar
  • 298
-2 votes
2 answers
136 views

How to Measure the depth of a Hole by Dropping a Rock? [closed]

Let's say I have a rock and a stopwatch. I am standing on the edge of a deep hole or canyon, and can see the bottom. How would I go about measuring the depth of the hole?
Arrow's user avatar
  • 101
2 votes
1 answer
60 views

Ultrasonic pulse in tube produces two reflections

I have an interesting problem which after much research I can not find any answers. I have an ultrasonic transducer sending a $500 \,\mu\text{S}$ $48 \,\text{kHz}$ pulse into a clean $20 \,\text{mm}$ ...
mpcengineer's user avatar
0 votes
0 answers
25 views

Problem with calculating the variance of different sounds

Problem: In a layered crystal with weak connections between layers, the dispersion law of acoustic backgrounds has the form $$\omega _1=s_1q_{||}, \ \ \omega _2=s_1q_{||}, \ \ \omega _3=Sq^2_{||},$$ ...
Dmitry's user avatar
  • 101
0 votes
2 answers
20 views

Question about Proportionality in Sound Equation (Pressure and Displacement Amplitude)

Why is intensity in terms of pressure amplitude inversely proportional to density and velocity: $I=\frac{\Delta p_\text{max}^2}{2\rho v}$, while in terms of displacement amplitude, it is proportional ...
Mato's user avatar
  • 19
0 votes
2 answers
60 views

We know that people can hear whether the water is hot or cold from the act of pouring, but have we ever considered the shape and material of the cup? [closed]

We know that one can hear whether water is hot or cold from the act of pouring, which is related to the viscosity of the water, the column of air inside the container, and the overall vibration of the ...
no rice糊糊's user avatar
2 votes
0 answers
23 views

Validity of approximations in the derivation of sound waves from Newton's laws

In deriving the wave equation describing the displacement of air in the atmosphere usually some assumptions about the displacement function $\chi(x,t)$ are made. For example Feynman says: Now in ...
slow thinking's user avatar
2 votes
2 answers
49 views

Confusion between two equations for sound intensity

The definition of sound intensity is $I=P/S$, where $P$ is the power generated by the wave source and $S$ is the area over which the energy is transferred. Assuming conservation of mechanical energy ...
Mikołaj Nowacki's user avatar
2 votes
1 answer
75 views

How does the chain rule work in sound wave analysis using fluid mechanics? $\tfrac{d x}{dt}\neq v$?

Context: I am reading Landau & Lifshitz's book on Fluid mechanics. Specifically its section on Sound waves. In section 101, the book's authors discuss about nonlinear traveling waves in one ...
asal's user avatar
  • 23
0 votes
0 answers
22 views

Sound radiated by wind instrument

My understanding of how a wind instrument (modeled as a tube open on both ends) works is as follows: Person blows into one of the open ends to create pressure waves. These pressure waves are ...
antoine's user avatar
  • 411
0 votes
0 answers
25 views

Resonant frequency of multi diameter closed pipe

I'm trying to make sense of how resonances in pipes work. I gather that, in the instance below, the fundamental resonant frequency of the 1m closed pipe (ignoring end correction etc.) is $$ f_{0} = \...
Buff Fox's user avatar
8 votes
4 answers
2k views

How does energy become sound?

From my understanding energy and matter are interchangeable ($E=mc^2$). Also, motion requires energy, but energy does not require motion. Now, for my question, as an example, I will use the chain of ...
Emotion's user avatar
  • 205
3 votes
1 answer
87 views

Reflection coefficient: Acoustics vs Mechanics

I recently tried to derive the reflection coefficient $R$. This is not a complicated task, however after making some literature research I found two derivations which arrive at seemingly different ...
Lockhart 's user avatar
0 votes
0 answers
23 views

Is the $n=0$ antinodal line in a double slit experiment constant loudness at all points?

If we assume a normal double-slit experiment with two speakers that produce identical sound waves, is the $n=0$ antinodal line going to have a consistent loudness wherever point on it? As the crest ...
Woo Luke's user avatar
1 vote
0 answers
11 views

Dependence of pitch on airspeed in vessel istruments

Why, unlike Helmotz resonance's model, does blowing more or less strongly vary the pitch of the note produced in a vessel instrument, like ocarina? Obviously the model is very simplified and ...
Falcon's user avatar
  • 11
12 votes
2 answers
854 views

Loudness unit, as logarithm of mean squared?

I've come across RMS in a variety of fields. I've come across dB units in a variety of fields. Right now I'm looking at an algorithm for determining the perceived loudness of an audio track (EBU R128'...
TrisT's user avatar
  • 273
1 vote
1 answer
49 views

Do wavenumber pairs exist for standing waves?

The equation for a travelling wave is usually taken in the form of, $$y = A\mathrm{e}^{i(kx - \omega t)}$$ When a standing wave is formed by the interference of two counter-propagating waves, then it ...
Alucard Nosferatu's user avatar
1 vote
1 answer
53 views

How to justify sound propagation is a linear time-invariant (LTI) system?

Background A linear time-invariant (LTI) system (black box) is one described by the system: \begin{align} \dot{\xi}(t) & = A\xi(t) + B\omega(t), \; \xi(0) = 0 \label{eq-abc-1}\\ \lambda(t)...
César VB's user avatar
  • 151
0 votes
1 answer
48 views

Mysterious sound from measurement setup in "zero measurement"

Once a colleague showed me a sound measurement setup in a reverberation room, meant to measure (unwanted) sound from magnetostriction in ferrite cores. There was a problem creating a true "zero&...
Jos Bergervoet's user avatar
6 votes
3 answers
620 views

Difference Between Particle Velocity and Wave Velocity in a Longitudinal Wave

In a longitudinal wave, both particle velocity and wave velocity occur in the same direction. It might seem intuitive to assume that the particle velocity should be identical to the wave velocity, ...
Arjun Raj's user avatar
  • 117
1 vote
1 answer
51 views

Why and how white noise cancels other background noises?

This idea of white noise cancelling other background noises is quite popular these days and I always wonder how it works? https://www.youtube.com/watch?v=nMfPqeZjc2c This is a sample of white noise. ...
Devansh Mittal's user avatar
0 votes
0 answers
28 views

Derivation of Lighthill Equation

I'm trying to understand the meaning of Lighthill equation. Based on my text book (sound and source of sound, Dowling and Williams 1983), it is derived from combining mass conservation and momentum ...
Kinnikuman's user avatar
0 votes
0 answers
41 views

Head-on collision of $\rm N_2$ and $\rm CO_2$ molecules [duplicate]

Consider a standing sound wave formed in the air in conditions close to standard pressure and temperature in the antinode region. On the molecular level, it will involve multiple collisions of air ...
Stan Tarka's user avatar
2 votes
3 answers
62 views

Why does air vibration produce a spherical wavefront and not a plane wavefront?

I want to know why the back-and-forth vibration of a material produces a spherical wavefront, for the produced sound wave, and not a plane wavefront.
Arjun Raj's user avatar
  • 117
0 votes
1 answer
64 views

How can I determine sound speed of ions in plasma sheath

Since the definition of sound speed, ($c_{s}$), in each ion s$th$ species ($is$) expressed that: \begin{align*} c_{s,is} = \sqrt{\frac{k(T_{e}+T_{is})}{m_{is}}}. \end{align*} How can we determine ...
nirama_xox's user avatar
0 votes
0 answers
40 views

Sonic boom on atomic particles

we know that something travelling faster than the speed of sound creates a continuous sonic boom because the air cant get of its way fast enough but if we consider smaller particles which can travel ...
Advik Pathak's user avatar
5 votes
2 answers
921 views

Ultrasonic whistling

My friend from physics who doesn't know whistling says he is good at whistling, but the resonant frequencies are ultrasonic so others cannot hear it. Could this be right, or is he just bluffing? ...
AlphaLife's user avatar
  • 12.3k
1 vote
0 answers
42 views

Echo in front of a periodic building

Hello, I recently found out that walking in front of a building leads to a strange echo (and so does clapping). The noticeable thing is that the facade of the building looks like a flipped staircase (...
Jean Pégoud's user avatar
0 votes
0 answers
27 views

Comparison between wave equation theory and transfer function theory

I deal with analysis of acoustic signals in solids. And after some literature research in physics and mathematic, I have a question about the followings two theories: Wave equation theory: Imagine I ...
Ronghua Xu's user avatar
3 votes
3 answers
102 views

What's the limit on the length of string that can be pulled by a person? [closed]

Imagine it's pre-industrial times, and a king wants to keep control of his vast empire. One of the biggest problems was how slow it was to transmit information; it could take weeks to be notified of ...
Reuben Matthews's user avatar
0 votes
1 answer
39 views

How wave speed affects perception?

If there were 2 sound waves with the same wavelength and amplitude, but different speeds, how would my perception of the waves vary? How would my perception vary if they were light waves instead of ...
VV_721's user avatar
  • 133
1 vote
2 answers
61 views

EM wave emission from earphone wires due to varying current signal

if we listen to some audio signal on a wired earphone, then does the wire of the earphone act as a transmitter antenna to emit the audio signal as radio waves even though its strength might be ...
sab's user avatar
  • 23
2 votes
0 answers
35 views

Frequence vs speed of a moving object

Imagine swinging wood stick using hand (say it's a 1-meter long cylinder with 2 centimeter diameter, just for the sake of argument). When doing it fast (angular velocity = $\omega_1$), it will create ...
h218614's user avatar
  • 21
0 votes
1 answer
31 views

If a damped mass-spring oscillator is equivalent to a resonant bandpass filter, then in audio signal terms, what is the input signal for both?

Background I am working on some personal audio processing and synthesis experiments in the sample domain. I posted here about how a resonant bandpass filter with a given $Q$ and frequency $f_0$ is ...
mike's user avatar
  • 321

1
2 3 4 5
56