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Questions tagged [acoustics]

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0
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1answer
49 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 ...
2
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3answers
494 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 ...
5
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7answers
2k 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 ...
1
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0answers
52 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 ...
2
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1answer
33 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 ...
0
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1answer
29 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, -...
1
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1answer
166 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 ...
0
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1answer
176 views

How to measure acoustic pressure level under water with a hydrophone?

this is my first post here and I am also new in signal processing. Let's say I have a hydrophone with amplifier which is connected to a sound card plugged in to a computer. I gather the sounds to a ...
1
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1answer
75 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? ...
0
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1answer
41 views

Why do third-octave bands have a ratio of cube root of two?

Without sounding tautological, I guess it boils down to the definition of the third octave, which is not: 2/3*Fc but defined as the cube root of 2 ratio between frequencies. Why is a third-octave ...
0
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2answers
49 views

What to do for the right FFT in Matlab (two peaks and incorrect amplitude)?

This is the FFT I'm using. But two peaks (did not expect the one in the beginning) are occurring and the amplitude is not as specified (expecting a value of 2). Any help is much appreciated! ...
0
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1answer
126 views

Measuring acoustic phase difference between two receivers

I am trying to measure the acoustic phase difference between two sensors 30cm apart each other. The sampling frequency is 20kHz, and my interest frequency is about 1700 Hz. The below is how I ...
0
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1answer
66 views

Channel Shortening for underwater acoustic channel communication

I'm new in this forum, hope that we can learn from each other well. I need to ask about the channel shortening for underwater acoustic channel. what are the common algorithms in that field? is ...
2
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0answers
94 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 ...
0
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3answers
85 views

Acoustic waves propagation distance relation with carrier frequency?

In electromagnetic waves, the energy formula is $E=hf$, that means frequency increasing will increase energy and so on the propagation distance. In underwater acoustic waves, low frequencies can ...
3
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0answers
67 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 ...
1
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1answer
128 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
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1answer
122 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
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2answers
70 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 ...
0
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1answer
401 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 ...
0
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1answer
26 views

How to model airborne sound channel

I'm making a soft demodulation/decoding to communicate a microphone and a speaker in short range. I have to calculate the LLR using my constellation and the airborne sound channel probability density ...
0
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0answers
34 views

Applying the inverse FFT to even out a room's sound - What is the more efficient algorithm?

I have a way (the standard way) to correct for my room's acoustics, but I'm wondering if there's a more efficient algorithm, something that doesn't involve going to the frequency domain maybe? I ...
0
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1answer
137 views

Is Phase Locked Loop is essential for BPSK signal reception?

I'm noob in DSP studying BPSK communication between speaker and microphone using acoustic signal. I read article of this BPSK communication which says it needs Phase Locked Loop(PLL) sequence to match ...
0
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2answers
328 views

What is the main difference between the acoustic and electromagnetic waves?

For simulation purpose, what will be the difference between using acoustic and electromagnetic waves? Just the carrier frequency only??
3
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3answers
3k 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 ...
2
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0answers
104 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 ...
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0answers
38 views

Confusion related to Room Impulse Response equation in a research paper

This paper presents a toolbox to simulate Room Impulse Responses (RIRs) based on Image Source Method (ISM). The equation (1) has a windowed sinc function in it, which is given in equation (2). I was ...
2
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1answer
199 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" ...
1
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2answers
767 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]) ...
0
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1answer
7k 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!
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0answers
68 views

How to convert multi-band Energy Time Curve (ETC) to Impulse Response (IR)?

I am running my own sound simulator. Now I have obtained the Energy Time Curve (ETC, expressed by energy) by physical simulation, and they are stored in 8 discrete frequency bands (because decay of ...
0
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1answer
188 views

What is homogeneous noise field?

What is the formal definition of homogeneous noise field? Is there any example of it? Thanks.
3
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2answers
298 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 ...
1
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1answer
237 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
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2answers
44 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?
0
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1answer
299 views

Calibration - acoustics

I have one recorded signal (.wav) and the calibration signal (.wav - 94dB @ 1kHz). I want to know how to calibrate the recorded signal using the calibration signal, for example, in Matlab. My tasks ...
5
votes
2answers
767 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) \...
2
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0answers
478 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
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1answer
195 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?
2
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1answer
85 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 ...
0
votes
1answer
1k views

I have a pressure signal and want to do SPL analysis on it

Signal I have an acoustic signal from a Ffowcs Williams Hawkings CFD analysis and would like to convert it to the frequency domain and see the SPL and OASPL. I know I need to use fft() but I am ...
3
votes
1answer
115 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 ...
0
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0answers
117 views

White noise sound vs harmonic sound reverb

I use a microphone array to localise a sound source in a small lecture theatre. I tested it with white noise and a bird noise source. I found out that the white noise source give very good results. ...
3
votes
1answer
164 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 ...
0
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2answers
654 views

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

I have been working on Active Noise Cancellation in real time for Air vent in kitchen. Initially for the demonstration purpose, I am using sinusoidal sound ( 40k Hz Fs,1000 samples, 2 kHz frequency, 1 ...
2
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2answers
93 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 ...
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0answers
13 views

Acoustic characteristics of thoracic diaphragm

I am looking for any kind of information about the acoustic characteristics of the thoracic diaphragm. In particular, I'm looking for characteristics which will allow to differentiate it from other ...
3
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1answer
75 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 ...
1
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1answer
289 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 ...
0
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0answers
138 views

MATLAB band-stop filter design for room reverberation?

I took acoustic measurements of a room using sine swept method, and I also used Pioneer sc-37 to obtain more accurate data. I used RoomEQ wizard software and measured the impulse response of the room,...