Questions tagged [spectrogram]

A spectrogram is a time-varying spectral representation (forming an image) that shows how the spectral density of a signal varies with time.

Filter by
Sorted by
Tagged with
0
votes
1answer
230 views

How to compare the syllable extracted from the audio

I need to recognize just one bird. I am trying to compare the syllables extracted from the sound samples. As a result of the spectrogram function, the power spectral density is taken from the sound. ...
0
votes
1answer
2k views

Frequency Spectrum with c++

I have written a script to plot the frequency spectrum of a sinusoidal signal with c++. Here are the steps 1-Applying Hanning window 2-Apply FFT using fftw3 library I have three graphs: Signal, Signal ...
1
vote
1answer
8k views

Python - time frequency spectrogram

I have some 64 channel EEG data sampled at 256Hz and I'm trying to conduct a time frequency analysis for each channel and plot a spectrogram. The data is stored in a numpy 3d array, where one of the ...
0
votes
0answers
151 views

Frequency range of acoustic feedback

What is the frequency range in which acoustic feedback can be found? Most importantly, is there some lowest frequency below which one can expect not to find any feedback? My conclusion from the ...
0
votes
1answer
491 views

Why does the specgram of this simple sine wave look strange?

I'm trying to test some intuition using the matplotlib specgram routine. I first generate a simple sine wave ...
2
votes
1answer
104 views

Extracting original signal from overlapping area

Considering this image, where I have a spectral decomposition of a light bulb. Due to the non point shaped light source, the spectral decomposition using a diffraction grating in front of my camera ...
0
votes
2answers
6k views

Get spectrogram matrix without specgram in MatLab

I have a signal in Malab, and I need a matrix, probably transposed specgram matrix without using specgram tool. Is it possible?
0
votes
3answers
988 views

Drawing a Spectrogram off of FFT - what are the decibels relative to?

I am trying to draw a spectrogram from FFT data I get from audio files. The problem is that I can't figure out is what the yielded power (decibels) are relative to. I'm getting some arbitrary -100db-...
0
votes
1answer
90 views

Are there any pictures of a sample accurate spectrogram on the web or in books?

I programmed a sample accurate spectrogram some time ago and i still have never seen a picture of another one. It's interesting maths, i was told it's trivial, so why has no one else posted research ...
4
votes
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 ...
0
votes
1answer
4k views

Reconstructing time domain signal with Hanning window

I am currently working on a frequency domain real-time application on a digital signal processor. Currently for one time frame of my algorithm I read in time domain data into a buffer, perform a ...
1
vote
0answers
505 views

Converting musicg spectrogram output to dBFS

I'm trying to convert musicg Spectrogram output to dBFS. With 16-bit signed integer PCM audio, and an FFT length of 2048, I'm trying to analyze the spectrogram for an audio file to determine things ...
0
votes
1answer
785 views

Strange phase spectrum from stft

I've tried to implement STFT in functional way in Python. I've got code such as below: ...
0
votes
2answers
930 views

Spectrogram of a chirp and its FFT

This question follows from an answer to this other question: Conceptual question on FFT and chirp signal I wrote a code starting from the spectrogram to compare it with the FFT result. ...
10
votes
1answer
5k views

Creating a spectrogram

I've been trying to work out the logic for this task, and plan to use the KissFFT source package to perform the fast fourier transform. Please let me know if this looks about right: Allocate an FFT ...
0
votes
3answers
549 views

Choosing the best measure for machine learning on a Spectrogram

I am working on an application to classify Talas(a piece of music with onsets). For that, I have the spectrogram of a Tala, which I want to compare with the test Tala, or compare 2 Talas. For this I ...
0
votes
1answer
89 views

Developing a classifier for a periodic music

I am trying to develop a classifier for Indian Taals, for which I would be focusing only on the Tabla. Now once a extract a period of the Tala(a repetitive pattern), I want to develop some feature ...
0
votes
3answers
664 views

Rendering a spectrogram of audio data - resulting magnitudes are all too close together

I'm working on creating an application which will render a spectrogram of the audio in an MP3 file. I'm having some trouble, though - after running the audio samples through my program, the resulting ...
3
votes
5answers
12k views

generating spectrograms in python with less noise

I'm trying to do something similar to Shazam (paper here) in Python. Basically the idea is to use FFT with sliding window to transform both WAV files and recorded audio to the same spectral ...
0
votes
1answer
1k views

Frequency resolution

I have made a stft_func in MATLAB which takes window length i.e t_short as a parameter for window length. Now, this function is ...
0
votes
0answers
378 views

Looking for an algorithm that computes weighted average of frequencies intensity from narrow band in spectrograph

I am searching for the algorithm that takes (audio) signal as an input and outputs weighted intensity of the frequencies of some narrow band (axis X) in time (axis Y). Frequency in the middle of that ...
5
votes
1answer
1k views

Spectrogram Analysis

I have four .wav files and each contain bird chirps. Given an input .wav file, I need to find out which bird it is. I have some basic understanding of signal processing. I have used spectrogram to ...
0
votes
1answer
325 views

Given a spectrogram, how do I calculate loudness over time?

I want to calculate the loudness of a given sound over time (like, in a graph) from its spectrogram. Can I do this from the spectrogram or is it better to do from the raw sound?
1
vote
0answers
383 views

Understanding PCA

OK, I have tried to ask the same question in the math site on stack exchange but no real joy. Apologises I'd this is the wrong forum. I am trying to compute the PCA of a spectrogram.. It is 486x128 ...
3
votes
1answer
114 views

Compressing A Range Of Decibel Values to One “Representative” Value

Don't have any formal dsp experience - sophomore in college. Working on constructing a 25 band bark spectrogram for psychoacoustic analysis of audio FFT data. To do this, I'm grouping all FFT ...
0
votes
2answers
1k views

Spectrogram - Am I missing something?

I have the following signal: I'm trying to compute a Spectrogram algorithm, but, don't think I'm doing it right.. I have computed the following: 1) STFT (size 256 with an overlap of 128) 2) ...
2
votes
1answer
136 views

Detecting a curve with certain characteristics in a spectrogram

I have a spectrogram built by breaking a signal into chunks and taking the FFT of these chunks. An example spectrogram is: In this spectrogram I am looking for a curve (aka pitch contour) that: ...
5
votes
5answers
2k views

Vertical lines noise in spectrogram

I have started looking into DSP and made an implementation of short-time fourier transform, using kissFFT to perform the FFT. I then render a spectrogram. An example image that I have generated can ...
0
votes
1answer
344 views

How to obtain the Spectrogram of a signal

I am trying to use Matlab to compute the spectrogram of a signal but I can't seem to figure out how Matlab computes the spectrogram.Consider the case where I have a ...
1
vote
1answer
987 views

PSD - Is this formula correct?

Trying to understand whether or not I am calculating the PSD correctly. Below is the equation that I am using: $$ PSD_{rms}(f_{m} = m \cdot f_{res}) = \frac{PS_{rms} }{ENBW} = \frac{2 \cdot \left | ...
3
votes
3answers
584 views

strange phenomenon in spectrogram of Windowed Fourier Transform [edited] [closed]

I am trying to understand how the Windowed Fourier transform works, so I used Matlab to create an artificial signal, and plotted the Windowed Fourier transform using a gaussian window. $x(t) = \left\...
7
votes
2answers
6k views

interpret wavelet scalogram

My knowledge of wavelets is less than epsilon. Bear with me. If I have a signal of two well separated sinusoids (15 and 48 Hz) plus some random noise, I can clearly make out the two in a spectrogram (...
1
vote
3answers
682 views

Will the resulting spectrogram from this algorithm be 1D or 2D?

I'm implementing a spectrogram algorithm and I get the basic concepts, however, I'm struggling with something. Let's say I have a 1D vector: ...
1
vote
1answer
4k views

How can I compute a time-frequency cross-spectrum in MATLAB?

MATLAB has a spectrogram function for the time-frequency analysis of a single signal. It also has a cpsd function for estimating the cross-frequency spectrum for two signals. However, cpsd averages ...
0
votes
1answer
343 views

STFT computational burden

I have a signal with length of $N$. The sampling frequency is $f_s$. Window size is $w$ The noverlap size is set to $m$. And $nfft$ is selected for frequency resolutions. I am running a STFT with ...
0
votes
1answer
852 views

Spectrogram from Complex Morlet wavelet ( recreating article result from data)

I am trying to recreate the following results: ...from the following data: Dropbox Link (FS40.dat) The time is in milliseconds (frequency is 40000 Hz) The article state that they used Complex ...
0
votes
1answer
612 views

I can't figure out why spectral features are “displaced” on a spectrogram

I'm trying to create a spectrogram of a complex signal 'y', but I'm running into a problem where the spectrogram that I create appears to have its spectral features "displaced" in frequency space, and ...
1
vote
1answer
257 views

What information is lost, if any, in normalizing Seismic/Earthquake time-frames in an STFT to equal variance?

This might be more of a statistical question, but let us assume that we take a spectrogram, or STFT, where time is on the x-axis, and frequency is on the y-axis in this matrix. What information might ...
0
votes
1answer
921 views

Gammatone filter vs 2D FFT for spectograms

I am working on speech segeration and each source I am reading , spectograms are being made by filterbanks which uses gammatone filters . I can't find a proper c++ source code which would make me ...
2
votes
2answers
170 views

Estimating noise level without 'quiet' segment

I have a signal which consists of an onset and a release period. The onset, sounding like a thud, excites frequencies across the entire frequency range (0-22 kHz). It lasts for about 0.1 s. The ...
1
vote
1answer
5k views

Spectrogram of wav file

I am calculating spectrogram of a audio file of 36 second using the following code snippet: ...
1
vote
1answer
6k views

Applying FFT to PCM stream

I would like to use a .WAV file and convert it into a spectogram. Any idea how to do this with Naudio? Basically the flow should be like this, I think: Convert WAV file to PCM stream Convert PCM ...
1
vote
1answer
3k views

Programming language for sound manipulation [closed]

Having had little experience in PHP, I moved to C++ in-order to create a spectrogram, I wanted to create probably the simplest/easiest one for my first project, so easy infact I don't need reading/...
3
votes
2answers
128 views

What is the theoretic difference in the ways to compute the spectrogram?

I have noticed that the spectrogram for a audio signal is often calculated in different ways when the result from the DFT is transformed into real numbers; some tend to compute $|k|$ or $|k|^2$ while ...
3
votes
0answers
261 views

Points of interest in a spectrogram

We have several audio tracks, all of which are different versions of the same track under one type of distortion: the speed of the track is increased by a constant factor K (hence frequences are ...
4
votes
1answer
1k views

Convolving With half-Hanning

The goal is to get a 200ms decaying delay of an audio signal while preserving the sharpness of attacks to mimick human perception of sound. The paper I'm following convolves a 200ms half-Hanning ...
2
votes
2answers
1k views

Finding the frequencies given in a wav file

I have a wav file containing a series of chords, each containing 3 or 4 notes, played concurrently. I need to find the frequencies of each note in each chord, and I can use matlab to do any ...
1
vote
1answer
2k views

why is the spectrogram from matlab different from audacity

Something related Here are the spectrogram plots: Matlab version: Audacity version: the darker parts towards the right of the figure show speech. Silence was added to the left of the figure in ...
2
votes
1answer
6k views

Please help me analyse spectrogram

I am working on noise reduction and I need to learn how to analyze spectrograms I mixed a pure speech file with violet noise in audacity and got the following spectrograms: Matlab version Sonogram ...
1
vote
3answers
392 views

When should I use a frequency spectrum rather than a spectrogram representation?

It seems to me that the spectrogram representation of a finite signal gives you significantly more useful information than a frequency spectrum. As I understand it, the spectrogram breaks down the ...