10 votes

Is sound the best way to transmit a signal under water?

Yes, it is called acoustic communications. Iterative Carrier Frequency Offset and Channel Estimation for Underwater Acoustic OFDM Systems is an example of a paper that uses orthogonal frequency ...
  • 2,172
10 votes
Accepted

MUSIC Algorithm for Direction of Arrival (DOA) in Acoustic Signals

The steering vector basically applies the delay according to the spatial location of the Uniform Linear Array (ULA). The multiplication by the complex exponential basically applies the delay. The ...
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7 votes

Acoustic waves propagation distance relation with carrier frequency?

For a sine wave of amplitude $A$ and frequency $f=1/T$, its energy from $-T/2$ to $T/2$ is $A^2T/2$. Thus the power depends only on amplitude. The energy over one period does depend on frequency, but ...
  • 5,835
7 votes
Accepted

What is the (approximate) function for amplitude of a plucked string over time? Does it differ between string types?

An exponentially decaying envelope $a\exp(-b x)$ is a good choice, and is used for example in vintage Yamaha FM synthesizers. It has the favorable property that over any constant length time interval, ...
6 votes

Sound absorption coefficients for frequencies higher than 8kHz and lower than 80Hz?

The main reason why the tables don't have it, is that it's hard to measure. The measurement technique in ISO 354:2003 relies on measuring the difference in reverberation times in a reverberation rooms ...
  • 33.8k
6 votes
Accepted

What is the best method for measuring of room reverberation time?

Well, there is plenty of ways for approaching this problem. Which one is best depends on room itself, your resources and pursued accuracy. I think that best way to start is to look into ISO 3382-2:...
  • 10.7k
6 votes
Accepted

How to change speed of audio samples without changing pitch?

This question (about "time-scaling" audio) is closely related to pitch shifting, which is time-scaling combined with resampling. But changing the speed without changing pitch is only time-scaling, so ...
6 votes
Accepted

Can I have some feedback on this research paper?

Comments provided here are in two broad categories: Presentation and Subject matter. The "Presentation" section is the easiest to address. There are some things that could be rephrased in terms of ...
  • 10.1k
6 votes

Is sound the best way to transmit a signal under water?

Yes, actually sound waves are better than RF signal in underwater, because of the low frequency requirement. We don't covert sound waves to radio signals. The transceiver in this case is called ...
  • 665
6 votes
Accepted

MUSIC implementation in Pyroomacoustics library

Why the Code Works It's important to note that the MUSIC algorithm works on the microphone array dimension only. So it doesn't care how the data on the receive channels (microphones in this case) has ...
  • 890
5 votes

Is sound the best way to transmit a signal under water?

You have 3 ways of communicating underwater 1) Acoustic : Most popular means of communication. Has high latency but good range 2) Low frequency RF. To increase the range you have to lower the ...
  • 51
5 votes

Is sound the best way to transmit a signal under water?

The best way for underwater communication is to be acoustic communication where sound waves are used. Sometimes, visible light is used such as red and green, but in all cases, acoustic communication ...
  • 1,046
4 votes
Accepted

What is the difference between undersampling and oversampling in analog to digital conversion ?

Good question as you can actually undersample and oversample at the same time! See my "DSP Puzzle" question on that specifically here: How do you simultaneously undersample and oversample? To best ...
  • 38.3k
3 votes
Accepted

Using all-pole filter to model the Room Impulse Response

It's not because of reverberation. When you want to model the Frequency Response of the room, it's common to simplify your approximation by using either all-pole or all-zero models. You don't want to ...
  • 10.7k
3 votes
Accepted

How many samples per cycle(time period) is actually enough to reproduce the sine wave sound properly?

It depends on how good your interpolation between samples is. If you have really good interpolation, anything more than 2 samples per cycle will suffice. This is not just a theoretical fact, it is ...
3 votes
Accepted

Double the "speed", double the frequency?

White noise: sounds exactly the same if you play it back at double the speed Stack up diminished fifth starting at a low enough fundamental (say 20 Hz). Play back at double speed: sounds exactly the ...
  • 33.8k
3 votes
Accepted

How is LMS/FXLMS noise cancelling different than simple polarity inversion?

Your polarity inversion method simply applies the same phase shift (delay) and gain to all frequencies, and is presumably not adaptive (or even closed loop). It may work reasonably well for some ...
  • 3,292
3 votes
Accepted

Is Phase Locked Loop is essential for BPSK signal reception?

There are three different kinds of synchronization in a passband digital communications system: Carrier synchronization: the receiver needs to know the exact frequency and phase of the carrier used ...
  • 13.9k
3 votes

What is the (approximate) function for amplitude of a plucked string over time? Does it differ between string types?

To a first approximation, a plucked string has an exponential decay, so your envelope will look like $$x(t) = a \exp -bt.$$ The physical explanation for this is simple: when you pluck the string, you ...
3 votes
Accepted

What are the limitations of using Magnetic induction rather than acoustic communication in underwater communication

Actually, magnetic induction is a current research topic for underwater communications, see http://bwn.ece.gatech.edu/papers/2015/j14.pdf. Also, this paper includes a nice comparison of underwater ...
3 votes

RMS level from impulse response

Please refer to Parseval's theorem. If your impulse response is $h(n)$ and its DFT is $H(k)$, then $$\sum_{n=0}^{N-1} |h(n)|^2 = \frac{1}{N} \sum_{k=0}^{N-1} |H(k)|^2 $$ So the square root of the sum ...
  • 409
2 votes

Convolving Room Impulse Response with a Wav File (python)

It is a little late, but i'm also working on convolution reverb at the moment. If it is still of interest, you can use my code. Simply call the function convolution_reverb and pass the paths to the ...
2 votes
Accepted

Convolving Room Impulse Response with a Wav File (python)

The way you read the files is a little odd. The method used here is clearer with respect to the sampling rate and the signal. You will note that the above example calls pcm2float after reading. This ...
  • 2,180
2 votes
Accepted

How does mic combined with loudspeaker work?

By using Acoustic Echo Cancellation. Since the signal that goes to the speaker is known you can subtract it out at the microphone, provided you know the exact transfer function from speaker to ...
  • 33.8k
2 votes

Proof from wave equation of upper limit of active noise cancellation

I don't have a mathematical proof for you, but here are 2 issues to think about. The impulse response from the actuator (speaker) to the error measurement (microphone) is non-minimum phase. This is ...
2 votes
Accepted

What acoustic properties of sounds enable us to distinguish the owner of the voice?

Some possible perceivable differences might include: differences in pitch frequency (bass vs. soprano voice, etc.) differences in overtone series (formants, head resonances, accent) variations in ...
  • 34.1k

Only top scored, non community-wiki answers of a minimum length are eligible