All Questions
Tagged with signal-processing acoustics
59
questions
7
votes
5
answers
2k
views
How exactly does a seashell make the humming sound?
My little brother asked me where the ocean-like sounds came from inside of a sea shell. I told him that the air trapped inside the shell vibrates, making a sound. But then he asked me why the air had ...
- 12.5k
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 ...
- 145
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)...
- 151
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 ...
0
votes
0
answers
20
views
FWHM and Beam Width of transmitted beam of ultrasonic (ultrasound) transducer
Im a studying ultrasonic transducer and I got a question about FWHM and Beam Width while solving some problems.
In the lecture, I learned that Beam width is calculated by:
$2\Delta\theta = \frac{3.8\...
- 43
10
votes
6
answers
3k
views
Can sound waves be modulated?
Can you modulate sound waves? Like can you have a sound wave of a relatively low frequency and modulate it with a sound wave of a much higher frequency which people cannot hear and send it through the ...
- 101
0
votes
0
answers
24
views
Is the strongest acoustic signal always the closest?
I have a single beam echosounder that I use to measure the distance to an object underwater. It emits an acoustic pulse and listens to the reflections. Using the time of flight and the strongest ...
- 1
22
votes
12
answers
8k
views
How do computers store sound waves just by sampling the amplitude of a wave and not the frequency?
All of this just doesn’t make sense though.
I mean, doesn’t the amplitude represent the loudness and the frequency the pitch? Aren’t they completely independent from each other?
Is the book just ...
- 390
12
votes
3
answers
4k
views
Avoiding radar detection using active noise control instead of a stealth fuselage
was reading about different stealth technologies used by modern aircrafts to avoid radar detection.
Wouldn't it be easier to have a receiver on the airplane listening on the radar frequencies and then ...
- 131
1
vote
0
answers
84
views
Modeling an Acoustic Reflection from a Wall
I am trying to simulate the reflection of a sound ray, that goes from a sound source, bounces off a wall, and is received by a microphone.
The wall has a an absorption coefficient, and a specular ...
- 11
0
votes
1
answer
143
views
What is the physical meaning of the pressure of an acoustic point source being complex?
Context
From various sources of Acoustics (such as "Acoustics -
An Introduction to Its Physical Principles and Applications" by Allan D. Pierce and "Fundamentals of General Linear ...
- 1,785
1
vote
1
answer
213
views
Why don't podcasts played at faster speeds sound higher-pitched?
Many podcast apps allow you to listen to podcasts faster than the speed at which they were recorded (typically at x1.25, x1.5, x1.75, and x2 speeds).
If these apps are simply replacing the sound's ...
- 48.3k
0
votes
1
answer
57
views
Can multi-instrumental sound be reconstructed from a waveform?
This question came about when I saw someone wearing clothing with a waveform on it. I wondered if it would be possible to reconstruct the original sound from the printed waveform.
I understand that a ...
- 101
2
votes
3
answers
516
views
Why does audio signal amplitude always fall off at higher frequencies?
In the frequency spectrum of every real audio sample that I've ever seen, the amplitude of the frequency components is always higher at low frequencies, then rapidly falls off at higher frequencies.
...
- 1,004
7
votes
2
answers
555
views
What do I hear when listening to a computer-generated sine wave?
When I use a sine-wave generator (such as this one), I give credit to the software and my hardware that a pure sine wave is produced (as close as is technologically possible) — that is, no harmonics. ...
- 173