# 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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### How to make sense of audio file's $\textrm{dBFS}$?

I'm trying to build a song visualizer using the FFT method. When I analyze the audio, I get the $\textrm{dBFS}$ value for each frequency range. From my understanding, $\textrm{dBFS}$ is in the range ...
124 views

### pyo: Retrieve amplitudes of audio signal frequenciy ranges

I'm playing around with audio signal processing for the first time and just to start somewhere, I decided to use the Python library pyo. My goal is to analyze an audio input signal from the microphone ...
138 views

### Real-time mixing of two audio clips while only modifying the data of one

Problem I want to mix two audio sources in real-time: game audio and microphone audio. The audio is provided at 44 100 Hz in the form of vectors of 1024 numbers between $-1$ and $1$ (PCM data). The ...
43 views

### Visualise/compare numpy arrays from Matlab/Octave to matplotlib

I'm new to python and matplotlib, and I'd like to visualise / compare 3 mfcc files stored as numpy arrays in txt format. I have the Octave code below, and I'd like to know how it can be done using ...
23 views

### How would I approach implementing a windowed sinc filter with changing cutoff in real time?

I moved this out of another question, where I'd put it to give more context, and answered it here for the next reader. ELI5 how to implement a windowed sinc FIR filter in real time for an audio ...
3k views

### Measuring Audio Signal Similarities

I have recorded samples of lungs sound (person breath) signals from electronic stethoscope. How can I measure (In percentage) the similarity between two audio signals (lung sound), the general idea is ...
1k views

### How to deal with audio with different length in Audio Classification

Currently, I am trying to work with the Dataset UrbanSound8K to try some Audio classification. And I got stuck in the preprocessing step already. Since the audios are of different lengths, like 4 ...
15 views

### Microphone Data Comparison for breathing data… best way to compare two files?

I am currently trying to compare the amplitude vs time data between two different microphone readings (.wav files of inhales and exhales) and detect which reading produced a louder sound, on average. ...
25 views

### Role of oversampling within resampling / pitch modification

I'm working on a pitch modification plugin involving resampling, and want the quality to be as high as possible. I currently use windowed sinc interpolation and lowpass filter where required. I ...
36 views

### When applying analog and digital effects on an audio signal is it better to start with a clean digital signal or use the analog effects before ADC?

If I am digitally capturing an audio signal from an analog source and I know I will want some analog effects applied, is it better to use them on the analog signal before doing the ADC, or should I ...
93 views

### How to make ultrasound audible?

Because of interesting spectral phenomena, I would like to shift the >20kHz content of my audio recordings to audible frequencies, so that I can listen to it. I tried the Audacity pitch correction ...
41 views

### Chirp zero crossings

I am generating a linear chirp in C code with a f0 , f1 and T. What is the most efficient way to solve where the zero crossings appear? Thanks
9k views

### numpy.correlate and autocorrelation; audio signal

I want to calculate delay between an input and an output audio signal of my audio processing system. The input and output signals are available as signed 16 bit integers. To try out, I tried the ...
28 views

### Time delay of direct path in RIR measurement

I am trying to measure an RIR using my laptop and a JBL Flip 5 speaker. I have tried, both, the Matlab tool and a python code shared on gihub. My final goal is to compare with the image method and ...
68 views

### Specify minimum trigger frequency for recording audio in Python

I'm writing a script for sound-activated recording in Python using pyaudio. I want to trigger a 5s recording after a sound that is above a prespecified volume and frequency. I've managed to get the ...
55 views

### How to extract noise from a signal in order to get both noise power and signal power

I have to implement a function to get an accurate SNR value. For that, I would need a separate noise signal to get the signal power and noise power but I have only one noisy signal (a .wav file.) ...
8 views

### Sound activated recording in Julia

I'm recording audio with Julia and want to be able to trigger a 5 second recording after the audio signal exceeds a certain volume. This is my record script so far: ...
56 views

### Is there a way to convert audio to a list of frequencies preserving the temporal position?

I want to convert an audio file to a list of frequencies. We can apply an FFT on the audio to gain analysis of all the frequencies in a given audio sample, however, I want a list of frequencies as a ...
106 views

### What is a “pitch period”?

The term pitch period appears in the book Speech and Language Processing by Daniel Jurafsy: As we just said, a pitch-synchronous algorithm is one in which we do something at each pitch period or ...
72 views

### Extracting audio segments based on detected onsets using libROSA

I have a couple of .wav audio files with very similar percussive signals whose onset times I can identify using libROSA's onset detection. I would now like to extract the associated audio segments ...
41 views

### Why does the volume increase when I reduce the gain of an all-pass filter connected in series?

I am using the colorless allpass-filter proposed by Schroeder Manfred R to create a reverberator. It consists of about 8 colorless allpass-filters connected in series, each with a different delay ...
101 views

### Popping sound after using bandpass filter

I'm trying to create guitar Wah Wah effect (basically band pass filter with dynamic frequency range). I'm using Steinberg SDK for it. I refactored this code to work in real time and it looks like this:...
53 views

### Why use both a high pass and a low pass filter in a Butterworth implementation for noise reduction?

I am a new to audio processing . I want to develop an application that reduces audio noise using a Butterworth filter. I found some existing code doing this, but I still do not understand the use of ...
98 views

### Can an audio recording tell whether it is made in a large or small room?

The conversation of one or more people will be analyzed. I think need to look for something similar to reverberation or echo in an audio signal. How can this be implemented? Update: small room is ...
112 views

### Sound activated recording and advanced filtering on Raspberry Pi

I'm making a Raspberry Pi bat detector using a USB-powered ultrasonic microphone. I want to be able to record bats while excluding insects and other non-bat noises. Recording needs to be sound-...
287 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 ...
37 views

### How common are audio effects that process a signal as a whole, rather than each buffer separately?

I'm writing a VST plugin using the JUCE library, and the way it is set up is that you can write a block of code to process buffers as they are fed to the program, one by one, meaning the program has ...
27 views

### Differentiate betwee sibilant “sssh” voice sounds and instruments like hi-hat?

How would I differentiate betwee sibilant "sssh" voice sounds in a music track and a similar sounding instrument sounds like hi-hat or cymbals?
999 views

### How to edit audios so that they have the same length

I have a dataset of audio files, which differ on their lengths by a couple of milliseconds. Some are little shorter than 1s and some are little longer than 1s. They all have the same sampling rate, ...
35 views

### Invertible overlap-summation of a vector

I'm using the Nonstationary Gabor Transform (https://github.com/grrrr/nsgt) for a DSP application. It has a sliced transform, called the sliCQ. Background: https://www.sciencedirect.com/science/...
179 views

### Phase difference calculation between two wave files

I am doing comparison between two wave files, How to calculate phase difference between those files? Second wave is generated by making some changes in the first one .I have tried calculating phase ...
49 views

### Karplus-Strong with Jaffe-Smith sample rate-independent

I tried to implement the Karplus-Strong algorithm with some of the Jaffe-Smith extensions (improve pitch, dynamics, etc). Here is the code. When I run it with a sampleRate of 48000Hz, I get very ...
59 views

### 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 ...
650 views

### Realtime sample rate conversion

Is it possible to have a realtime sample rate conversion in a way that a peer A with an audio stream at 44.1 KHz sends it signal over the network to another peer that is on an audio stream at a 48 KHz ...
349 views

### Signal and Space/Time

I have been reading a couple of definitions on signal such as: Any quantity measurable through time over space or any higher dimension can be taken as a signal. And this, In the physical ...
2k views

### What's the impact of aliasing in the time domain?

I've been studying digital audio and come across something I can't understand. There appears to be something like a consensus (among those capable of understanding such things) that the impact of ...
71 views

### Is there any deterministic downsampling algorithm for audio?

I was trying to use the scipy.decimate function provided in the library, but I had a question - I want a pre-processing algorithm to downsample audio in such a way ...
244 views

### Is it possible to use a Volterra series to generate subharmonics?

Taylor series can create harmonics of the frequencies in an input signal. I'm wondering if it is likewise possible to use Volterra series to create sub-harmonics of the frequencies in that signal. ...
211 views

### Where do RBJ's analog shelving filters come from?

In RBJ's Audio EQ Cookbook, the analog prototype for a low shelf filter is given as such: H(s)=A\cdot\frac{s^2+\left(\frac{\sqrt{A}}{Q}\right)\cdot s + A}{A\cdot s^2 + \left(\frac{\sqrt{A}}{Q}\right)...
49 views

### far field and near field definition for microphone array

What is the definition of far-field and near-field in acoustic sensor / microphone array? Does it depend on the distance or the power of the sound?
221 views

### How do audiobook players manage to quickly speedup/slowdown playback speed without using more memory?

Many audiobook player apps on Android have a reading speed slider which lets us choose the reading speed e.g. 0.5x 0.75x 1.00x 1.25x 1.50x. This is time-stretching ...
45 views

### Balance Fader in Digital Amplifiers

What is the purpose of Balance / Fader in a digital Audio amplifier? In a signal flow what is the most apt position to place balance and fader(for example after before a compressor unit or at the ...
37 views

### Why does my zoom audio, when there are nearby microphones, seem to usually take an open loop format?

The signal from the speaker on device A gets into the microphone from device B, then the amplifier and then the speaker from device B, back into device A. The result is a sort of runaway signal that ...
32 views

### Amplify filtered smooth brown noise to range [-1.0f, +1.0f]

I am trying to make a "noise generator" like Pioneer example here. I am using a smoothed brown noise and passing it to a bandpass filter to achieve this noise in C++. For smooth brown noise. ...
82 views

### Audio Equalization, Is Parallel or Cascade better

I'm not really an audiophile, so I can't determine the difference. I was playing around with Matlab's Graphic EQ and I noticed that there is a difference in the Magnitude response for the same gain ...
65 views

### Generate Smooth Brown Noise Mathematically

I have a sound engine where I feed float PCM values between -1, +1. I am trying to make a noise generator. I want to be able to generate brown noise Mathematically as float PCM valaues so that I can ...
116 views

### How to compute key of a song?

I'm looking for a precise way to compute the key of a song. BPM would be cool too. Analog is ok. I tried to approach it from the DFT angle, but got stuck and can't really put a finger on what's the ...
93 views

### Can lossless audio be wirelessly transferred via Bluetooth?

I have a question that is that possible to wirelessly transfer lossless audio via Bluetooth? Please help me explain technical reasons behind it such as the size of the the lossless data, the maximum ...
98 views

### How to generate a noise like Pioneers white noise?

I am making a music app and I want to put a noise generator in it. The problem is the usual white, pink noise is just too boring and not useful for the user. Pioneer mixers has an amazing noise ...
62 views

### Frequency response of a long signal

I am trying to get the frequency response of a system, so, in theory I would need to do: H = fft(y)./fft(x); I have measured the system with a long stepped sine ...