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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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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890 views

Designing a lowpass filter to minimize aliasing in pre-decimated streaming audio

I need to apply low-pass filter to PCM files. There are several methods such as FIR filters, IIR (butterworth-chebyshev..) filters but it seems to me applying Fast Fourier transform and eliminating ...
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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 ...
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1answer
5k views

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
5k 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 ...
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Can you turn a square wave into a sine wave using a low pass filter?

And if it could, would it make the sound of the square wave thinner than before because of losing its harmonics?
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2answers
870 views

Difference between jpg compression and mp3 compression

My understanding of jpg compression is that, if done repeatedly, any image will eventually be reduced to a single flat color, due to the way it deals with neighboring pixels. However, years ago I was ...
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5answers
9k 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 ...
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3answers
828 views

Digital delay effect: avoiding clicks on delay time change

I'm implementing a digital audio delay effect using a simple circular delay line. Changing the delay time by making the delay line longer or shorter introduces discontinuities in the audio signal, ...
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6answers
3k views

Does it make sense to have complex numbers representing real-world audio signals?

In this course (Coursera: Audio Signal Processing for Music Applications) the professor uses an example of obtaining the DFT of a complex sinusoid: \begin{align} x_2[n]&=e^{\jmath\left(2\pi f_0 n+...
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4answers
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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 $y(t)$ ...
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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
9k views

Taking audio frequency and picking out peaks (Peak Detection)

So I have a unique challenge. I want to take an audio file, and pick out the peaks in the samples and plot that onto a graph. Each point based on the amplitude/pitch(?) will be represented as either a ...
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3answers
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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 ...
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1answer
319 views

Morphing between two FFTs

I'm a musician and I'm making a script that takes a wave file and snaps each of its frequencies from the fourier transforms to the nearest musical harmonic. Thanks to help from another question I ...
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4answers
3k views

How to recognize patterns in a noisy audio frequency spectrum?

I have an audio spectrum (FFT) that looks like this: ...
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1answer
151 views

Bandwidth expansion by computing missing harmonics in music?

In old recordings or highly compressed audio files (lossy), the higher frequencies are lost, and we hear a distinctive muffling effect. (Just like if the song was played through a wall) Is it ...
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1answer
2k views

How do I construct input to neural network from audio signals?

Input: Microphone recordings of digits from 0 to 9 from different speakers. Output: The digit from 0 to 9. I am doing this for fun. So first I will train my neural network using some samples and ...
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3answers
2k views

How do impulse response guitar amp simulators work?

I am wondering how impulse response guitar amp simulators/modelers work. I thought it was a matter of convolving a signal of recorded impulse response in time-space with a guitar sample. I tried to ...
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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 ...
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3answers
8k 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....
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3answers
6k 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 ...
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2answers
294 views

Is there any way to make a sampling rate reduction in the frequency domain?

Is there any way to take advantage of the frequency domain to make a clean/nice sampling rate reduction effect ? and how ? Basically, deducted from my tests: if I set to 0 the magnitude uppon a ...
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2answers
251 views

How do the English pronunciations of “tiu” and “tou” differ?

I'm creating an app (I'm a software developer) that for different sounds (interjections from the user) will do different things. For example if the user says: "Tiu", than it will do task A, if it ...
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1answer
633 views

RMS values above 0 dbFS?

I wonder why several RMS meters I'm using for music production show RMS values above 0. For example, when using an input signal with a constant DC of 1 (0 dbFS), I get these results, although ...
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2answers
4k views

How to stitch together MFCCs from multiple frames?

I am trying to record a sound two times and compare the two recordings. I am playing exactly the same sound both times (for example, play a small .wav file twice and record it each time), so I hoped ...
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5answers
304 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 ...
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2answers
9k views

Simple beat detection algorithm for microcontroller

For the purpose of controlling DIY disco lighting, I'm looking at implementing beat detection in a microcontroller with limited computing power (i.e. Arduino Uno). While detecting all beats would be a ...
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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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2answers
949 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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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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1answer
63 views

I trigger recording when power of current sample is X dB greater than last Y samples, what is the terminology here?

Doing time domain processing of incoming audio. I sample the power level every 0.25s and keeping a running average of intensity over 5 samples. When the power level of the current sample is 10dB ...
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1answer
4k views

Voice Audio Detection algorithm

I have to detect speech intervals in large pre-recorded files in my project. I think, there won't be so much noise in the background (audio will be recordered in the room or even in the studio), but ...
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1answer
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The Bode frequency shifter

Anyone know if the Bode frequency shifter has been studied somewhere. I just used an audio plug-in called EchoBode from SonicCharge and this is claimed to use a frequency (pitch) shifting algorithm ...
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2answers
424 views

How to detect continuous noise in audio call?

We want to detect bad audio quality in audio call. Should we extract this information from amplitude or frequency spectrum ? Is there any technique/transform/filter available for this ? Example: I ...
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1answer
5k views

Signal filtering using Python

I'm trying to create an application using python that is capable of recording an audio signal and detecting short glitches in the signal. For example, I could be recording a 1000Hz sine wave and ...
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1answer
190 views

How to create a sine wave that transitions through frequencies and returns to phase

For an auditory psychological experiment, I need to create a sine wave, such that at a given point the frequency of the wave will rise smoothly, and descend back to base frequency. I need it to return ...
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6answers
1k views

Find Short Clip of Audio Within Longer Clip Of Audio

I need help figuring out a way to automatically synchronize two audio files that are both different recordings of the same source. More info below. This example is from a concert, where there is only ...
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4answers
12k views

Note Recognition Software

I'm wondering if anyone knows of any open source solutions to note recognition. I'm planning on building a program for online sheet music, which recognizes your notes, and tries to tell you what you ...
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2answers
317 views

Audio DSP HW Recommendation

I'm very new to DSP hardware, so I am taking it upon myself to learn it with regard to Audio and Acoustic Signal Processing. I've learned quite a bit of theory in a graduate DSP course, but absolutely ...
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2answers
401 views

how to extract telephone audio only from an mp3

I have mp3s of radio talk shows in which the host interviews people on the phone. The host uses a microphone, and the interviewee uses either a landline phone or a cell phone. I want to save just the ...
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1answer
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Demodulating FSK audio in Python

I am trying to write a Python script that can demodulate an FSK modulated audio file and return the data encoded in the audio. The data being transmitted is GPS NMEA strings which are embedded as the ...
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2answers
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STFT overlap add method - What am i doing wrong?

i am trying to implement a short time fourier transform of an audio signal to do some filtering (subtract another stft signal using spectral subtraction). I am using a hamming window function with 50% ...
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1answer
245 views

Teager's Energy Operator

Does anyone know how to find information on the derivation (rather than the definition and application) of Teager's Energy Operator, both for the continuous and sampled case. I have Kaiser's early ...
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0answers
623 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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4answers
903 views

Noise reduction using multiple recordings of the same signal

I have two (audio) recordings of one analog signal, I used two separate devices (smart-phones) recording from two different locations. Each recording device is pretty crappy, lot's of electrical hum ...
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4answers
17k views

python; audio; detecting silence in audio signal

I have real-time audio application written in python, and I have question about detecting silence. What's the most efficient way to distinguish silence from non-silence, in an input audio signal? By ...
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3answers
685 views

Signal processing for audio and speech

I have started learning about signals and I am interested in sound signals. There are some questions that I need to resolve. For example in music, difference of notes like 'sol' and 'la' are about ...
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1answer
525 views

Why did my sine wave turn into a square wave when written to a WAV file in Octave?

I am trying to use Octave to generate a pure sine wave. The code for the same is as follows: x = 10.*sin(2*pi*(300/16000)*(0:1:400)); The sampling rate is ...
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2answers
417 views

How can I measure the harmonicity of an audio spectrum?

I would like to estimate the "harmonicity" (harmonics-to-noise ratio ?) of an audio signal from its spectrum. What kind of algorithm can I use?

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