Questions tagged [audio]
Audio, or in terms of signal processing, an audio signal is an analog or digital representation of sound, typically as an electrical voltage.
129
questions
4
votes
1answer
1k views
Compensating Loudspeaker frequency response in an audio signal
I have been working on a project in which I was required to work on the audio signals recorded from the loudspeaker kept in front of a filter. So, to simply explain it:
$$\boxed{\rm LoudSpeaker} \...
10
votes
2answers
2k views
How to deal with low fundamental when using AMDF for pitch extraction?
I am using the Average Magnitude Difference Function to estimate the fundamental frequency of a quasi-periodic audio signal. The AMDF is defined as
$$ D_n = \frac{1}{N-n}\sum_{k=n}^{N-1}|S_k - S_{k-n}...
60
votes
8answers
95k views
How do I implement cross-correlation to prove two audio files are similar?
I have to do cross correlation of two audio file to prove they are similar.
I have taken the FFT of the two audio files and have their power spectrum values in separate arrays.
How should I proceed ...
27
votes
5answers
16k views
How to create a sine wave generator that can smoothly transition between frequencies
I am able to write a basic sine wave generator for audio, but I want it to be able to smoothly transition from one frequency to another. If I just stop generating one frequency and immediately switch ...
11
votes
3answers
12k views
How to resample audio using FFT or DFT
I'm down sampling voice audio by first performing an FFT, then only taking the parts of the result that I need, and then performing an inverse FFT. However, it's only working properly when I'm using ...
51
votes
10answers
33k views
Algorithm(s) to mix audio signals without clipping
I'd like to mix two or more PCM audio channels (eg recorded samples) digitally in an acoustically-faithful manner, preferably in near-real-time (meaning little or no peek-ahead).
The physically "...
19
votes
4answers
23k views
Reconstruction of audio signal from Spectrogram
I have a set of songs for which I extracted the magnitude spectrogram using a Hamming Window with 50% overlap. After extracting the spectrogram, I did some dimensionality reduction using Principal ...
43
votes
5answers
57k views
What is the difference between phase delay and group delay?
I'm studying some DSP and I'm having trouble understanding the difference between phase delay and group delay.
It seems to me that they both measure the delay time of sinusoids passed through a ...
27
votes
6answers
2k views
Calculating the PDF of a waveform from its samples
A while ago I was trying different ways to draw digital waveforms, and one of the things I tried was, instead of the standard silhouette of the amplitude envelope, to display it more like an ...
12
votes
2answers
11k views
Add odd/even harmonics to signal?
How do I add odd or even harmonics to a floating point signal?
Do I have to use tanh or sin?
What I'm trying to do is achieve some very simple distortion effects, but I'm having a hard time finding ...
34
votes
9answers
12k views
Is there an algorithm for finding a frequency without DFT or FFT?
I was looking in the Android app store for a guitar tuner. I found a tuner app that claimed it was faster than other apps. It claimed it could find the frequency without using the DFT (I wish I still ...
28
votes
4answers
37k views
Hilbert transform to compute signal envelope?
I've heard that the Hilbert transform can be used to calculate the envelope of a signal. How does this work? And how is this "Hilbert envelope" different from the envelope one gets by simply ...
12
votes
4answers
19k views
Efficiently calculating autocorrelation using FFTs
I'm trying to calculate an autocorrelation on a platform where the only accelerated primitive I have available is the (I)FFT. I'm having a problem though.
I prototyped it in MATLAB. I am, however, ...
12
votes
2answers
1k views
Detecting drum bpm in a noisy .wav file
I am looking for algorithm(s) to solve the following problem:
Given a noisy .wav sound capture (some wind + friction noise on the microphone), how to detect the BPM of a soft drum beat?
I have ...
4
votes
1answer
2k views
Use MATLAB to Restore a Signal from a Given Degraded Signal Using Tikhonov Regularization
Anyone could share how to develop an application in MATLAB to restore the signal from a given degraded signal using Tikhonov regularization i.e restoring the signal $f$ via solving
$$
\min || g - f ...
6
votes
5answers
8k views
Equal power crossfade
I am working on an audio system where I need to implement an equal power crossfade between two signals over a specified number of samples. Initially I implemented a linear fade but this creates a dip ...
43
votes
6answers
45k views
Simplest way of detecting where audio envelopes start and stop
Below is a signal which represents a recording of someone talking. I would like to create a series of smaller audio signals based on this. The idea being to detect when 'important' sound starts and ...
4
votes
3answers
5k views
Reconstruction of Audio Signal from its Absolute Spectrogram
I have the absolute Spectrogram of an audio signals.
I lost the phase data of the Spectogram because of various processing applied on the original spectrogram of the signal.
I'm trying to reconstruct ...
8
votes
2answers
8k views
Help implementing audio dynamic range compression
I am trying to implement audio dynamic range compression in JavaScript (not using web audio API).
There is a lot of articles for sound technicians, and some high level documentation, but I couldn't ...
6
votes
2answers
14k views
What is spectral entropy?
Can anyone explain what spectral entropy is?
Does noise with a restricted bandwidth have the same spectral entropy as white noise?
6
votes
4answers
3k views
How to recognize patterns in a noisy audio frequency spectrum?
I have an audio spectrum (FFT) that looks like this:
...
5
votes
3answers
7k views
Generalized Cross Correlation
What is the definition of Generalized Cross Correlation?
I need it for estimating the delay (time offset) between two audio signals. The time offset between the two signals might be as large as 500ms....
9
votes
2answers
726 views
Filtering of streaming audio
Given something like 103 data points ($N=103$), a DFT will give back 103 frequency values. Then to do something like filtering the high frequencies involves setting the high frequency values from the ...
7
votes
1answer
4k views
SPL values from FFT of microphone signal
I am trying to get a frequency response vs dB SPL plot for recorded sounds. I have a microphone with a flat response, a sensitivity of 4mV/Pa, and 1 Pa = 94dB.
To get the dB SPL, I have the following ...
8
votes
2answers
2k views
Fast pitch recognition
I need to detect pitch (measure signal frequency) while the musicians play music, giving a warning if they are out of tune, but music happens to be a bit too fast for FFT (Fast Fourier Transform).
...
4
votes
2answers
3k views
Estimating the time offset (delay) between two audio signals in real-time
I'm looking for an algorithm which can accurately estimate the time-offset/delay between two audio signals in real-time. One audio signal is a loudspeaker signal and the other signal is the microphone ...
4
votes
4answers
8k views
How Can I Resample a Signal with an Arbitrary Factor (For Example - 128000Hz to 16000.1Hz) in MATLAB?
I need to simulate the sampling of a continuous (fsCtu = 128000Hz), acoustic signal with two microphones that have a slight offset in sampling rate (fsMic1 = 16000, fsMic2 = 16000.1) in Matlab. What ...
1
vote
1answer
216 views
Precise Centre frequency of an All-pole digital filter
I'm not an engineer and have essentially taught myself all I know - this present problem is giving me some problems.
I have an all-pole filter (a gammatone filter - impulse response is essentially a ...
0
votes
1answer
377 views
How can I find SNR, PEAQ, and ODG values by comparing two audios?
I have two audios, A and B. B is the noisy version of A. I want to know how much B is different from A.
Can I do this by calculating signal to noise ratio (SNR), Objective difference grade (ODG), and ...
5
votes
4answers
7k views
Calculate Phase angle between two signals i.e. digital Phase meter
I want to calculate the phase difference between the two channels(signals) of a stereo audio file.(uncompressed data i.e. PCM samples).
I want to determine whether whether two signals are in phase or ...
0
votes
2answers
3k views
Wav To Spectrogram, Back To Wav
Currently, I'm writing a Python script, which should do the following:
read an audio file respectively a wav file via scipy.io.wavfile.read().
calculate the spectrogram of given wav file.
write the ...
51
votes
4answers
23k views
Analogous Library to OpenCV for Audio Processing / Analysis
I understand OpenCV is the de facto library for programming image processing in C/C++; I'm wondering if there is a C or C++ library like that for audio processing. I basically want to filter raw waves ...
16
votes
4answers
28k views
Feature extraction for sound classification
I'm trying to extract features from a sound file and classify the sound as belonging to a particular category (eg : dog bark, vehicle engine e.t.c). I'd like some clarity on the following things :
1) ...
15
votes
2answers
11k views
How to extract vocal part from stereo audio signal?
I'm now processing MP3 file and encounter this problem. My MP3 is stereo encoded. What I want to do is extract vocal part for further processing(whatever mode of output signals, mono or stereo are ...
8
votes
1answer
2k views
Coloring a waveform with spectral centroid or by other means
Update 8
Unhappy of having to upload tracks to the service and looking at the new release of RekordBox 3 I've decided to take another look for an offline approach and a finer resolution :D
Sounds ...
8
votes
5answers
4k views
Piano pitch detection
I'm working on a piano tuning program and part of it requires real-time pitch detection. Here is the scheme I have so far which works to some degree but could probably use some refinement.
I'm ...
6
votes
4answers
915 views
Monotonic, symmetrical soft-clipping polynomial
Okay, I intend to answer this question myself, but I would like other folks to pipe in on it. The issues or requirements are this:
Input to soft-clipper is $x(t)$, output is $y(t)$.
Output $y(t)$ ...
10
votes
3answers
12k views
Digital Distortion effect algorithm
I read the DAFX book by Udo Zölzer about the distortion effect at pages 124-125
and it says that suitable simulation of the distortion is given by the function:
$$f(x)=\frac{x}{|x|}\left(1-e^{x^2/|x|}...
8
votes
1answer
8k views
Speech comparison algorithm for rating on similarities
I am trying to compare 2 speech samples and rate them on similarities. Think of someone trying to repeat a phrase, and then comparing those 2 audio files.
I started by implementing the MFCC (http://...
5
votes
5answers
284 views
Remove a known wav file from recorded file
I looked at many similar questions but still cannot find an answer to my problem.
I'm playing an audio file N, while recording a man talking (b).
The problem is that the microphone gets the played ...
5
votes
3answers
10k views
Is there any free software that can recognize and classify sounds?
i am making a smart home automation software and i would like to know if there is any software that can recognize noises such as speech ,playing music,phone ringing etc
The exact software i am looking ...
15
votes
1answer
7k views
Getting loudness of a track with RMS
I'm trying to calculate the loudness of an audio track I have stored in a buffer. The buffer contains PCM data of the signal and I want to get how 'loud' it is by using Root Mean Squared. I assume I ...
14
votes
5answers
2k views
Identify Where Singing Starts in a Voice Only Recording
I have a little karaoke-style app where a user sings 4 lines of a song, with a one second gap between each line. There is no backing music, so it's voice only, hopefully making the problem easier to ...
12
votes
3answers
18k views
How do I compare 2 audio files, returning a percentage of difference
Is there a way to compare 2 audio files, whereby a percentage of difference will be returned?
I am using C# VS08, .net framework 3.5.
Edited: difference in the sound (like for eg. Audio 1: ...
11
votes
1answer
4k views
Applying A-weighting
I want to calculate the loudness of a given signal and I've come across this thread. I'm slightly confused about the A-Weighting aspect of it. I can't post images, but I think this site has the ...
5
votes
3answers
6k 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
votes
2answers
3k views
What is the difference between pitch detection and Onset detection?
According to wikipedia Onset detection:
Onset refers to the beginning of a musical note or other sound, in
which the amplitude rises from zero to an initial peak. It is related
to (but ...
0
votes
1answer
517 views
How to detect and remove ringback-tone and ivrs voice etc from the beginning of an audio call recording
In an audio recording (say a telephone conv. b/w two people), how would I programatically detect and remove the dial-tone at the beginning of a call using python.
Ex :
As you can see the first 15 ...
8
votes
4answers
619 views
How to determine the “variability” in a frequency range?
This is a continuation of a previous question.
I'm trying to analyze breathing and snoring sounds, and while I can fairly well detect snoring now, breathing is a bigger challenge.
I've learned that ...
4
votes
1answer
945 views
What is the difference between PSOLA and TDHS time-scaling or pitch-shifting?
What is the difference (if any) between PSOLA (Pitch Synchronous Overlap and Add) and TDHS (time domain harmonic scaling) time-pitch modification algorithms?
