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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9
votes
1answer
246 views

How to segment phone call audio into silence/non silence?

My problem is that I don't know the energy of the background noise, so I can't just threshold the energy. The processing is done in real time, and I have about 500msec to decide. Ideally, I'd want ...
4
votes
1answer
508 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 ...
6
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4answers
2k views

How to recognize patterns in a noisy audio frequency spectrum?

I have an audio spectrum (FFT) that looks like this: ...
27
votes
4answers
35k 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 ...
10
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
2answers
261 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 ...
11
votes
3answers
20k views

Autocorrelation in audio analysis

I'm reading up on Autocorrelation, but I'm not sure I understand exactly how it works and what output I should expect. Am I right in thinking that I should input my signal to the AC function and have ...
7
votes
1answer
378 views

MP3 Decoding Discrepancy

Is it possible for two different decoders to output two different sample results for the same MP3? I'm decoding an mp3 on Matlab and it produces two columns (presumably one for each channel). When I ...
14
votes
2answers
5k views

What methods can be used to identify and remove echo from an audio system?

Background I am designing a system that will have a single small microphone and speakers for use in a phone type setting. Easiest example I can give is a Skype conversation where you are using your ...
3
votes
1answer
423 views

Am I handling offline FFT correctly?

I need some help clarifying FFTs and what they represent. I have a buffer containing compressed audio. Due to limitations, I can't handle the full uncompressed audio but can decompress small segments ...
14
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 ...
12
votes
1answer
529 views

Recognizing math functions within songs

I'm new to DSP, and just discovered this StackExchange, so apologies if this isn't the right place to post this question. Is there a resource that describes genres in a more mathematical terms? For ...
8
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4answers
4k views

Complex conjugate and IFFT

I asked a question over on stack overflow. I'm having a slight problem however. As suggested by Paul R I am mirroring my lower $n/2$ bins into the upper $n/2$ bins. I have a few questions however. ...
10
votes
4answers
446 views

Audio output quality

When a digital device (PC, portable media player, etc.) plays a digital audio file (ogg, mp3, flac, etc.) the audio signal output is always the same, regardless of the device type/brand, am I right? ...
41
votes
5answers
51k 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 ...
19
votes
6answers
767 views

What does one need to know in order to build a software synthesizer?

For someone who has some experience in software development, loves his synths and knows the [very] basics of digital audio representation, what are the first steps he should follow in order to program ...
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 ...
14
votes
1answer
1k views

Estimating onset time of a tone burst in noise?

What techniques might one use to estimate the onset time of a sinusoidal tone burst in a noisy signal? Assume the tone burst has a known fixed frequency (but unknown phase) and a very sharp rise ...
32
votes
4answers
10k views

What are good ways to detect signal clipping in a recording?

Given a recording I need to detect whether any clipping has occurred. Can I safely conclude there was clipping if any (one) sample reaches the maximum sample value, or should I look for a series of ...
58
votes
7answers
90k 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 ...
9
votes
3answers
3k views

How to check the FFT results of a sine wave?

I have been given an audio file (sine wave) 1000Hz as an input to my FFT algorithm. I have got 8192 power spectrum samples in a array. What is the best and easiest way to check whether my output is ...
12
votes
3answers
17k 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: ...