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
10
votes
1answer
721 views

What are thoughts on best modulation to use for underwater acoustic communications at low frequencies?

I wanted to ping the DSP hivemind for general thoughts on what would be the best modulation type to use for low frequency underwater communications. I have chosen this project since I can learn a lot ...
8
votes
8answers
3k views

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

Could sound be used in transmitting sound waves under water digitally? Could the sound then be converted by a repeater to transit by radio waves? What other ways can a signal be transmitted other than ...
7
votes
1answer
323 views

How do Phons relate to loudness?

Let's say I have the very same signal stored in 2 .wav files. And lets say I process each file using a function, and it is established that one file is 20 phons ...
6
votes
2answers
12k views

Calculation of Reverberation Time (RT60) from the Impulse Response

I have some confusions regarding reverberation time (RT60). I need to calculate reverberation time from a given power envelope. This is what I get. As you might see the line is curved close to zero (...
6
votes
3answers
7k views

How to change speed of audio samples without changing pitch? [duplicate]

This question may be more appropriate on music stack exchange but since sound is a branch of physics and this is more of a technical question relating to sound waves than a musical question I asked it ...
6
votes
2answers
2k views

What are reasonable levels for the ERLE (Echo Return Loss Enhancement) in acoustic echo cancellation?

I am working on acoustic echo cancellation which has a double talk detector. During the single talk, the ERLE (Echo Return Loss Enhancement) exceeds 100dB and during double talk around 20dB to 40 dB. ...
4
votes
1answer
2k views

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

I want to measure a reverberation time in the room. What is a best way to do that? What kind of signal should be used? I know about balloon and pink noise, but are there any better methods?
4
votes
1answer
2k views

Acoustic feedback detection algorithm

I am woking on an sound processing application where I have limited processing resources. I need to be able to detect acoustic feedback and then signal that such an event occurred. I am not concerned ...
4
votes
2answers
2k views

Double the “speed”, double the frequency?

Usually, when some sample is played-back at twice the rate it was recorded, the pitch of the recording sounds an octave higher. For example: $g(t) = \sin(2 \pi f t)$ and $g(2t) = \sin(2 \pi f 2 t) \...
4
votes
1answer
1k views

Calculating SPL from pressure signal - Amplitude vs Power method

I have a pressure signal from a Fluent FFowcs-Williams Hawkings acoustics analysis. I converted this pressure signal into the frequency domain in order to get SPL values, using Matlab. I used the ...
3
votes
2answers
443 views

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

I am building a matlab simulation that applies room compensation to a 3D audio rendering system, and I'm searching for the frequency dependent sound absorption coefficients of various materials in ...
3
votes
2answers
112 views

Dealing with echoes / dead-spots in digital transmissions

I'm looking at communicating digital data through the air as soundwaves. To illustrate the problem, I generate a 10-cycle 2kHz wave, play it out through my MacBook's speakers and pick it up on my ...
3
votes
1answer
230 views

Using all-pole filter to model the Room Impulse Response

Why is all pole model pretty useful in modelling room acoustics? Is it related to reverberation?
3
votes
1answer
92 views

Proof from wave equation of upper limit of active noise cancellation

Anybody know of a proof of the hard upper frequency limit of active noise cancellation using the ear canal volume as a boundary condition to solve for the upper frequency limit? I keep on encountering ...
3
votes
1answer
81 views

Artefacts from playing ultrasound through PA system

I encode data in audio by energising 5 frequencies between 17.5kHz and 19.5kHz: I play the ...
3
votes
3answers
173 views

Is it possible to “equalise” a signal by deconvolving the impulse response of the room in which it is to be played?

I am using a test sweep with a flat power spectrum and linear group delay (Optimized Aoshima's Time Stretched Pulse) to measure a room's frequency response. Having obtained the impulse response of the ...
3
votes
3answers
732 views

Impulse response with sweep from measurement

Does someone have a matlab script to get the impulse response from the recorded measurements using log sweep? I have the input file (sweep) and the output and I need to get the impulse response and ...
3
votes
1answer
135 views

Acoustic room simulation - Craven's hypothesis

I'm reading Udo Zölzer's "Digital Audio Signal Processing" and there's a piece about acoustic room simulation. This question will be more about maths and acoustics, but I assume anybody who does DSP ...
3
votes
1answer
184 views

Acoustical Design considerations for Active Noise Cancellation Project for Air vent

I am working on ''Active noise cancellation for air vent'' project. I am using NI myRIO1900, Audio Technica ATR 3350 omni directional microphones and Tevion Loudspeakers. I have done the programming ...
3
votes
1answer
172 views

Underwater Acoustic Positioning

I have to develop an underwater positioning system which has to determine the position of a ROV. Four buoys will be placed on each corner of a swimming pool. Each one of these buoys will be equipped ...
3
votes
1answer
183 views

Estimating harmonic loudness

I'm working with data that looks something like this: ...
3
votes
0answers
95 views

Energy Detection in Presence of Colored Gaussian Noise

Before asking my question, let me introduce the context: For spectrum sensing based on energy detection, which has been widely studied in presence of AWGN, the optimal detection threshold is computed ...
3
votes
0answers
188 views

Room Impulse Response Inverse Problem

This article here talks about a room impulse response generator which takes the source and destination coordinates, sound speed, sampling rate, room dimension and wall reflection coefficients as input ...
2
votes
3answers
691 views

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

Impetus: I'm currently working on my first synthesizer, after many years of playing with them. I've just added an ADSR envelope to modify the gain, but for some reason it sounds wrong to me. I've ...
2
votes
2answers
97 views

How does mic combined with loudspeaker work?

There is variety of loudspeakers on the market that have built-in microphone so that they can produce sound and perceive it at the same time (and do it surprisingly well). How they managed to ...
2
votes
1answer
516 views

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

Consider a noise-cancelling headphone: If I have a noise signal from the outside world, mic it, flip the polarity by multiplying by -1 (with an op-amp or digitally), delay by the appropriate amount, ...
2
votes
2answers
109 views

is there a second order approximation to perceived loudness

Quoted from this As a first order approximation it takes ten times the energy to double the perceived loudness So is there a 2nd order approximation. If so then how much change in RMS value ...
2
votes
1answer
35 views

Modes and wavetypes

I am studying results from vibration signals on rotating machinery, using two accelerometers. I am interested in dispersion characteristics. I have read that it is possible to identify acoustic '...
2
votes
1answer
112 views

GCC-PHAT for Multiple Sound Sources

Can GCC-PHAT be used to detect multiple time-delays (that is, having multiple acoustic sources simultaneously)? The documentation for the gccphat(sig,refsig) ...
2
votes
1answer
35 views

Why is the sound field intensity due to $K$ point sources given by $ I(p,\omega) = \sum_{k=1}^K \sigma_k^2(\omega) \delta(p - p_k)$?

I am trying to understand the following piece of text. I am not used to dealing with sound intensity and power so I'm not familiar with the derivation of the formula $(*)$ below. Statement: 1. We ...
2
votes
1answer
241 views

Autoregressive modeling (linear prediction) of electrical transmission lines?

I've read that the reflection coefficients in speech processing (as computed by the Levinson-Durbin algorithm for solving the Yule-Walker equations) "represent the fraction of energy reflected back" ...
2
votes
1answer
111 views

Looking for a way to monitor raw microphone digital output?

This is sort of a cross between a data processing and Physics question, but I would be grateful if anyone here could help me. My objective is to calculate the sound pressure level (in dB) of a sound ...
1
vote
1answer
149 views

Can I have some feedback on this research paper?

I have submitted this paper "Effect of Transducer Positioning in Active Noise Control" to arXiv. I would like to get some feedback on the methodology of the same. Inputs of any sort are welcome. Can ...
1
vote
3answers
4k views

Convolving Room Impulse Response with a Wav File (python)

I have written the following code which is supposed to put echo over an available sound file. Unfortunately the output is a very noisy result which I don't exactly understand. Can anybody help me with ...
1
vote
3answers
305 views

How to calibrate a signal with respect to frequency

I have recordings from accelerometers (non-flat response with respect to frequency) and I'd like to convert my voltage time series into acceleration values. Is there a standard method for doing this? ...
1
vote
2answers
88 views

Digital filter simulating hydroacoustic signal distortion

Preambule: I'm designing a sound model for my small submarine game. Model is running on the server, and I want to present the client with a mono-channel wav-stream from his hydrophone (20kHz ...
1
vote
1answer
4k views

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

When converting a signal from analog to digital, we observe undersampling and oversampling. Does oversampling means that the sampling frequency is greater that the signal's frequency and does ...
1
vote
1answer
16k views

dB/hz to dB Conversion

I'm have a PSD graph of dB/hz vs. frequency in hz. I want to convert the dB/hz unit to dB, but I can't find any way of doing it. Help would be much appreciated!
1
vote
2answers
46 views

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

Different people reading the same sentences, we can know from the voice who is speaking. What makes the voice distinguishable?
1
vote
1answer
31 views

relationship of frequency with range in Underwater acoustic channel

I am interested to know what range of frequencies can be used/ or are effective for wireless communication, within the underwater acoustic channel. I do know a table exists from \cite{...
1
vote
1answer
759 views

Explanation of OASPL and SEL

I have data of different SPL for different 1/3 center frequencies. Is it correct to sum the pressures at a mean square basis of those SPL values (and then convert them back to SPL) to obtain the OASPL ...
1
vote
1answer
182 views

sound source localization - finding source vector

This may sound a stupid question - but I am working on some simple microphone array beamforming sound source localization stuff. I think I understand how to use beamforming to find the TOA of the ...
1
vote
2answers
2k views

Pa^2/Hz to dB/Hz conversion

I have PSD data from an computational aeroacoustics analysis, which is in the units of Pa^2/Hz. I want to convert this to dB/hz; would it be correct if I use PSD[in dB/Hz] = 10log10(PSD[in Pa^2/Hz]) ...
1
vote
1answer
325 views

Frequency measurement from acoustic emission sensor data(VDC RMS)

Currently, I am facing a problem about understanding FFT concept and getting exact frequency with acoustic emission sensor data(VDC RMS data). I want to measure the sound frequency from the acoustic ...
1
vote
1answer
393 views

Normalize Fourier Transform For Video Game

I am in the process of developing a video game where I would like to sync a character's mouth with an audio clip of their speech that is playing. I found this great website that shows the profiles of ...
1
vote
2answers
107 views

Separate static echos from acoustic signal (ICA?)

I am using acoustic waves to measure the thickness of material. My problem is that the acoustical lens produces static echos in the signal. I try to separate both because there is a short interference ...
1
vote
1answer
114 views

Echo detection for localization

I was reading about active sonar and couldn't quite understand how the echos are recognized. My doubt is, when the sound signal is reflected back, it is greatly attenuated and distorted due to many ...
1
vote
0answers
33 views

Is fundamental frequency information present in speech-shaped white noise?

I am using a so-called speech-shaped stationary white noise, which means so much as a white noise that has been filtered to match the long-term spectrum of a female speaker. The way it was generated ...
1
vote
0answers
48 views

Underwater acoustic channel is giving me a flat BER vs SNR curve

I need to do OFDM and GFDM signal transmission in underwater acoustic channel. I have my underwater acoustic channel as follow. ...
1
vote
1answer
68 views

Should I pass Kalman Filter absolute or offset-from-mean sensor values?

I'm using Kalman filters to segment the loudness of an acoustic signal from surrounding noise. The problem I've encountered is that muffled or faulty microphones measuring 'silence' (-70dB, -69dB, -...