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.

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Decoding Matrix Encoded Surround Sound Through Convolution

I wish to create a finite impulse response filter to decode a dolby digital matrix encoded 2 channel signal into 5 channels. These filters would then be used in a realtime pipeline on a Linux machine ...
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1answer
2k views

Can you count signal energy equivalent in frequency domain?

I read about method of analyzing audio signals where FFT result is bandpass-filtered and the energy of this band is counted. Can you count the momentary energy in frequency domain? Does this mean ...
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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 "...
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4answers
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Most efficient way to extract frequency components of audio signal with near-human accuracy in real time

I'm trying to work out how (if possible) to extract the frequency components of an arbitrary audio sample (typically music) in an FFT-like manner, but in my research on the FFT algorithm, I'm learning ...
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2answers
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Calculating bpm from machine sound (not music)

I have a hydraulic breaker on a excavator that hammers with a dynamic bpm. I have recorded this sound so that it is in a mp3-file and would like to determine the momentary bpm for the length of the ...
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Linear predictive model convolution

Accidentally asked this question in the general area and was told to ask here, so... I've been trying to develop a lightweight, relatively-fast-to-decode sound compression format for use in my gaming ...
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2answers
431 views

Correcting large variable dc bias in signal FFT

I am somewhat new to signal processing, but i'm hoping I can provide enough information in order to be pointed in the right direction. I am working on analyzing the frequency spectrum of audio signal ...
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1answer
277 views

Stereo sound separation into three sources

Whenever we listen stereo songs, one part of the audio like voice hear at the center of the head, and other parts are nearby left ear and right ear. If I represent center part by C, and other parts by ...
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1answer
742 views

What features describe audio signals? (Besides frequency and amplitude)

I recorded sounds with a microphone and I try to distinguish them in my Java program. The frequency works quite good, but if I look at the fourier transforms it seems like there should be more ...
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1answer
88 views

Signals - Removing Blocks

I'm after some advice on a problem that I am facing regarding signal processing. I am processing a voice clip (.wav) and this voice clip contains noise, and I need to remove the noise and just ...
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3answers
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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 ...
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1answer
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Automatic Gain Control for voice

I am tasked with designing the logic for an automatic gain control. It won't be a traditional AGC in that it has to run on a computer and continuously modifying the volume is not possible in the same ...
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2answers
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Extracting audio track to determine the song beat

I'm completely new to this field. Perhaps I'm calling it by a wrong name, but I want to analyze an audio track and retrieve a timestamp to beat mapping. Is there an open source 3rd party library ...
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1answer
255 views

Audio Fingerprinting

I am doing the project in audio fingerprinting, in that after I convert the signal into mono, I have to apply the hanning window, the size of the window is 370ms, and I have to overlap the signal with ...
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1answer
3k views

Filtering PCM data in java

I'm working on an audio based application for android platform , I'm trying to use a low pass filter to a fixed or variable max frequency "depends on the cost of development". first I've been playing ...
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1answer
194 views

How to get started analyzing audio signals for detecting cracks in a material?

I have two processes, one is normal and the other with some cracks of material. And I have the acoustic signals got from the materials by a sensor. I want to compare these signals to see if this ...
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1answer
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Audio fingerprint questions

I am developing an application that requires audio fingerprints. I have been reading a lot of articles and PDFs, now i think i have gotten myself confused. Based on my present understanding, I have ...
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1answer
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voice recognition vs speech recognition MFCC

I have a basic understanding of the acoustic preprocessing involved in speech recognition: divide the speech into frames, find the mel frequency cepstral coefficients of each frame, construct a ...
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1answer
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Library to differentiate people by their voice timbre

Say there are 3 people in the room. Each of them have a unique voice timbre. I want to recognize people by their timbre and know who's speaking.
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1answer
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Plotting the magnitude response of a biquad filter

I've put together a multi-band audio EQ using biquad filters. I'm getting the coefficients using the methods from the RBJ cookbook. Now I want to plot the curve showing the magnitude response. I'm ...
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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 ...
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2answers
868 views

change the frequency component of a spectrum in an audio file

I am working on an audio dynamic range compressor using Matlab. After calculating the FFT of the audio file, I use several bandpass filters to amplify specific bands separately. What I want to do then ...
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2answers
173 views

Measuring the “frequency stability” of a signal

I'm thinking about ways to automatically identify and analyze lots of musical instrument samples, and would like to find the part of the sample that's the most stable in frequency, without any ...
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3answers
18k views

human speech noise filter

Does anyone know of a filter to attenuate non-speech? I am writing speech recognition software and would like to filter out everything but human speech. This would include background noise, noise ...
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1answer
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How to change volume of a PCM 16 bit signed audio?

I know I can multiply samples, then clip but perceived volume is non-linear for humans. Can you please help with a formula.
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699 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 ...
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2answers
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Loudness of PCM stream

I'm receiving PCM samples through stream which is one channel, 8000 samples per second. I figured out way of finding out loudness by calculating 'force' of signal by adding abs value of every next ...
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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 ...
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1answer
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How to make a silence?

I am trying to make a method in my simple application which is like SetSilence(); Now If I have audio (mono) PCM 16 bit Signed - should I fill all data with 0 ...
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1answer
837 views

Ultrasonic speaker calibration and emitting calibrated signals

I'm trying to calibrate an ultrasonic speaker with the aim of emitting predictable signals, but alas I keep running into trouble, probably due to my lack of DSP-fu. A little background I want to be ...
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2answers
912 views

How to prevent “zipping” effect on a modulated fractional audio delay line? (Flanger)

I am implementing a Flanger using a fractional delay line. I am modulating the length of the delay line using a sin function. The delay line already uses linear interpolation to compute the delay ...
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1answer
341 views

Recognizing data clustered into shapes

I am working on a project in Python to detect and classify some bird song, and I have found myself in a position where I need to convert a wave file into frequency vs. time data. This hasn't been too ...
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1answer
4k views

Audio normalization

I have a recording in pcm format and I want to do some simple analysis. I have some questions about what is normalization. As far I understand it is to get all the amplitudes between a range i.e. [-1,...
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4answers
2k views

Can FFT be used to find peaks and pits on audio files

I'm able to read wav files and its values. I need to find peaks and pits positions and their values. First time, I tried to smooth it by $\frac{(i-1 + i + i + 1)}{3} $ formula, then searching on ...
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1answer
1k views

What is the best way to represent audio visually? (x-post from UX)

Original Question: https://ux.stackexchange.com/q/23040/16006 I've only taken some basic signal analysis courses, so I might be missing some things. Purely theoretical question: What methods exist ...
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1answer
307 views

How to characterize the regularity of rhythm?

Again, my snoring detector: When I look at the rhythm of snoring vs the rhythm of talking in terms of peaks/events (which would represent snores) per hour, there's not much difference -- they range ...
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2answers
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Understanding values saved in WAVE file

The values that one can find in a wave file, e.g. 0.0036 0.0026 0.0174 0.0050 0.0026 0.0108 0.0154 -0.0114 -0.0006 0.0115 ...
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0answers
600 views

What is EAQUAL ? How does it relate to PEAQ?

This wiki post on wiki.hydrogenaudio.org says that it is very similar to PEAQ and also a part of ITU-R BS.1387 recommendation ? How reliable it is for determining audio quality. Are there any other ...
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1answer
1k views

Determining how similar audio is to human speech

While looking for an answer to this problem, I found this board so decided to cross post this question of mine from Stack Overflow. I am searching for a method of determining the similarity between ...
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2answers
899 views

differences in fundamental frequency/pitch between music and speech

I am developping a program, that extracts very expressive frames from a video (meaning: frames, which could summarize a video) for a university seminar. One of my ideas was, to analyze the audio data (...
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4answers
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Scipy - Audio Processing

I am looking for good tools for Audio signal processing. e.g Speech & music analysis, automatic language identification, etc. Does the Scipy library provide functions for audio processing? Does ...
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3answers
4k views

Output of KISS FFT interpretation

I'm receiving PCM data trough socket connection in packets containing 320 samples. Sample rate of sound is 8000 samples per second. I am doing with it something like this: ...
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Audio signal comparison for automatic singing evaluation

I am trying to compare audio waveform from input waveform (A) to preset waveform (B)from in the device. I try to lookup everywhere. Most likely someone give such a source code as follow : ...
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4answers
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Help with equations for exponential ADSR envelope

With application code, I have implemented a linear ADSR envelope for shaping the amplitude of an oscillator's output. The parameters for attack, decay and release duration as well as sustain level ...
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2answers
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What bandpass filter design will yield the shortest impulse response?

Designing a simple 2nd order IIR bandpass Buterworth filter with a centre frequency of 500 Hz and a 1 octave bandwidth gives me the following frequency response ... Now, if I take the impulse ...
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1answer
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Speech Compression - In LPC how does the linear predictive filter work on a general level?

Hi I'm taking a multimedia systems course and I'm preparing for my exam on tuesday. I'm trying to get my head around LPC compression on a general level, but I'm having trouble with what is going on ...
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1answer
531 views

What are the basic categories of operations performed on audio signals to create interesting sounds?

I don't know if this question will make sense as I'm very new to dsp. In my limited foray into audio dsp I've come across: Frequency Modulation Amplitude Modulation Additive Synthesis Subtractive ...
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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 ...
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3answers
19k views

Alias frequency Formula

I'm taking a multimedia systems class in my MSc Computer Science, and I'm having some trouble understanding the formula for the alias frequency - this could stem from my misunderstanding of the alias ...
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Libraries for Voice Activity Detection (Not Speech Recognition)

As follow up to my previous question I was wondering if there are any speech detection libraries in existence. By speech detection I mean passing in an audio buffer and getting back an index of where ...