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.
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What is the difference of calculating signal power that using these two methods: using moving average filter and using forgetting factor?
The conventional signal power calculation can be:
$$
P(n) = \frac{1}{N}\sum_{i=0}^{N-1}x^2(n-i)
$$
$x(n)$ is the signal. However, I have seen another method:
$$
P(n) = \lambda P(n-1) + (1-\lambda) x^2(...
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Implementation of dispersion compensation of lamb waves
I am trying to implement the method from Paul Wilcox paper "A rapid signal processing technique to remove the effect of dispersion from guided wave signals" on data from a lamb wave ...
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Improving the Time Domain Normalization of Acoustic Sound Data
I have tried to evaluate the analog microphone (IMP23ABSU) built into the STEVAL-STWINKT1B with the FP-SNS-DATALOG1 (HS-Datalogger). The values were exported as "raw values" (this is an ...
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From pressure to SPL : microphone calibration using sound level meter calibrator and sound level meter
I have a microphone + signal conditioner with adjustable gain and filter. I capture amplified signals using an oscilloscope. I'm using this signal to compute equivalent continuous sound level
With the ...
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How can sound waves be modeled in a manner that distinguishes individual voices but also recognizes words?
More specifically, I'm curious how we can represent sound waves in a way that would both distinguish between individual voices and also recognize, e.g. that recordings of different people saying the ...
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Comparing spectrogram similarity over time
I have a data set of spectrograms from moving audio recorders. As the recorders get closer, I expect the spectrograms to become more "similar". I expect this "similarity" to be a ...
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What effect causes this Pattern?
I've conducted a measurement of underwater noise in a laboratory experiment.
Therefore i am using a sweep signal.
Sometimes -I guess when the signal is much more louder- I get this fascinating ...
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Modeling an Acoustic Reflection from a Wall - a Paradox?
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 ...
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What does the frequency of oscillating microphone feedback depend on?
Pointing a microphone to a connected loudspeaker creates a feedback path and usually results in acoustic resonance, which manifests in a sustained oscillation: https://youtu.be/_XTtjZ8aZbc. A similar ...
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How to extract pressure values from a WAVE file?
Possible a duplicate but I could not find a direct answer. I used a sound card (Focusrite, at 96 kHz sampling frequency) connected to a calibrated hydrophone to record an ultrasonic signal, with a ...
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Modeling end-blown flute instrument using adaptive filter
I want to find the resonant frequency of specific end-blown flute called Persian ney, Using LMS in arrangement of system identification. Two signal is needed for algorithm:
system excitation (...
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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, ...
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Random Peak at the end Impulse Response
I am measuring a room's acoustic impulse response by playing a log sine-sweep through a speaker from 20hz to 24 khz, and then recording it using a microphone.
The sweep is 10 seconds long, followed by ...
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What additional inputs are required to convert dBFS to dB SPL?
It is probably very well known that dBFS cannot be directly converted to dB SPL without knowing other information such as the technical specifications of the microphone.
The questions are:
What is ...
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FFTs, Spectrograms, and Units
I am new to signal processing and I have likely a very easy question but I have found inconsistent answers everywhere.
When performing an FFT, does it matter what units the amplitude is in? Currently ...
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Troubleshooting distortion in room impulse response measurements:
I am collecting data for a project, where I am measuring the room impulse response by playing a sine sweep from a speaker (QSC K8 1KW Active Loudspeaker) and measuring it from the other side of the ...
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Phase Difference Calculation in Frequency Domain
I am currently working on an application in which I have a Linear acoustic array, the audio of which is analyzed using FFT. Now I also want to perform phase difference calculation and have also learnt ...
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MUSIC implementation in Pyroomacoustics library
I am currently using the multiple signal classification (MUSIC) algorithm provided by the Pyroomacoustics library in order to estimate direction of arrival angles and it works pretty well for both ...
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Definition of ERLE - echo return loss enhancement, measure when there is only echo?
A theoretical question in echo cancellation performance evaluation: $\mathrm{ERLE}$ = $\mathrm{E}$cho $\mathrm{R}$eturn $\mathrm{L}$oss $\mathrm{E}$nhancement, is defined as
$$
\mathrm{ERLE} = 10 \...
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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 (...
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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) ...
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Meaning of "standard deviation noises of wavelet coefficients"
I am currently working on a research project based on the paper titled A deep learning approach for anomaly detection based on SAE and LSTM in mechanical equipment. The paper uses data in the acoustic ...
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Realtime classification of (one of 12) vowel phonemes
I'm attempting realtime classification of (one of 12) vowel phonemes, sung (steady-state-ish) into a microphone.
MOTIVATION:
Suppose my user sings a MIDI note using a steady-state vowel phoneme (no ...
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Filter model of passive attenuation of headphones
It is possible to model passive attenuation of headphones as a Matlab/Python filter ?
For example I would like to find digital filter which will be simulating the way of the passive attentuation of ...
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MUSIC Algorithm for Direction of Arrival (DOA) in Acoustic Signals
I have seen multiple reviews of the MUSIC algorithm for the estimation of DOA. Most of those reviews consider a complex signal input with a complex steering vector. So, how do I implement this ...
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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 ...
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Simulated Room Transfer Function
I need help obtaining a simulated transfer function in a simulated room. I have created image sources for first and second order reflections, and am assuming a point source for my source. I have the ...
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2D Spatial Fourier Tranform on a pressure field
I'm doing some research on Fourier Near-field Acoustic Holography (NAH). The basic theory behind Fouerir NAH is that you take a sound pressure field measurement in a 2d plane p(x,y), 2d spatial ...
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Calculation of Reverberation Time (RT60) by interrupted noise method
As part of my thesis,I want to write in Delphi the algorithm to calculate the reverberation time using interrupted noise method. Delphi, Signal processing and accoustics are new topics for me. Room ...
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How to normalise 3D time-frequency sound intensity vector
I've got a 3D time-frequency sound intensity vector that I've derived from Ambisonic b-format signals. W acts as the sound pressure ...
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RT 60 from Impulse response
I have already the impulse response of an acoustic environment in the form of a series of signals over 300 samples. I have tried the procedure given in this platform - i.e. low pass filtering, Hilbert ...
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Calculation of ITD (Interaural time delay) using linear prediction - python
How is it possible to calculate the interaural time delay between two signals recorded underwater (ship sound signals)? Will linear prediction weight method be used for this?
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A way to estimate beat frequency from two audio sources
I am accordion repairer and also an engineer.
I plan to make a useful tool in Python to help with tuning.
In an accordion, there are several reeds making different sounds at different frequencies, and ...
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Estimating reverberant time (T60) of an IIR filter
I'm learning a method to genenrate pink noise by filtering a white noise in this book, and the author mentioned an estimation of T60 given the coefficients of an IIR filter in the code that
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How to apply an atmospheric attenuation filter in the freq domain and then convert the filtered signal back to the time domain?
This question is a part of a more general question the answer of which I don't know -
How to apply a filter in the freq domain and then convert the filtered signal back to the time domain? Well, I ...
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Indian Space Research Organization - Extent of spectral spread 1/3rd Octave Analysis [closed]
I am a scientist at Indian Space Research Organization (ISRO) and will be representing my team. We work on Telemetry and Data Handling units for our Launch Vehicles.
We are preparing for our upcoming ...
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RMS level from impulse response
I am trying to quantify the average differences between several impulse responses over the frequency range and over octave bands.
So, I am doing (in Matlab):
...
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sound source localization - calculation of sound intensity vector angles
I'm working on an acoustic source separation problem where I want to separate the voices of a choir based on intensity vector statistics.
I'm currently implementing a paper by Günel called “Acoustic ...
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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 ...
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Hydrophone kit to transmit (and receive) underwater
May I ask you if there exists a complete kit (e.g., by including the amplifier, etc.) of professional hydrophones to transmit and receive signals in underwater environments? If not, can I ask you for ...
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Echo Removal from PCM 16 bit arrays (time frames)?
I am keen to know the basics to remove echo knowing FarEnd Signal and NearEnd Signal. I have read research papers in which its commonly said:
y(n) = (hT)x
where h is the room impulse response and T ...
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Why use complex envelope to model raw measurements?
The usual answers when asking "why use complex numbers to model measurements?" is usually: (a) Because you are measuring a phenomenon like electricity and magnetism. (b) Because it is super ...
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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, -...
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Multiple short-range impulse responses aggregated to simulate a long-distance impulse response
I'm a biologist and I was thinking of ways that impulse responses could be used to simulate how an animal sounds over various distances in different types of forests.
Ultimately, if a tool was ...
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Estimate IR's from single channel speech audio
I have a dataset of single-channel audios containing speech, recorded in a single room. I need to extract the room IR's. The goal is to simulate the room acoustics and adjust new speech audios ...
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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 '...
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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 ...
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What do troughs represent in a sound wave?
What's the notion of negative amplitude? I hope the title and the question don't mean different things.
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What is the driving Voltage?
While I was looking into ultrasonic transducer in order to transmit and receive a beam, I came across specification of a transducer stating driving voltage as 20Vrms. I am not sure what actually does ...
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Statistics to characterize time-domain envelope of acoustic signal
I am interested in comparing 0.5-second 44100/s signals when different ADSR envelopes are applied to them. However, I don't want the comparison to be as fine-grained as simply calculating a 5000-...
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