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.

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How to modify spectrograms so that there is no effect of amplitude on their classification?

Is there any way to bring different classes of spectrograms to comparable amplitude levels so that when they are used for classification, the deep learning algorithm focuses on other aspects (like the ...
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Using spectogram to speed up a signal - Time Scaling/Phase Vocoder

Background About half a year ago, while learning about spectograms as part of an Image Processing course I took, I was told you can speed up audio using spectograms as follows: Calculate the ...
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Spectrogram of x,y,z data from accelerometer

Using scipy.signal.spectrogram for creating spectrogram and matplotlib's pcolormesh for plotting. I'm working on a project where I'm using a spectrogram to visualize the frequencies of the ...
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what the difference between spectral density and the power spectral density?

What is the difference between the spectral density and the power spectral density, Or they are the same thing? In fact, I find this term in the book of GODA 2000.
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How is 76 frames calculated mfcc for 1 sec signal with 25 msec window and 10 msec overlap?

I was studying about keyword detection and while doing some reading, I read we take 1 sec audio signal. We then divide it into 25msec sub sections with and overlap of 10msec. We apply mel filter bank ...
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Performing STFT after Butterworth Filter Seems Lower in Resolution

I have a signal recorded at 2MHz sampling rate. Before any decimation might be required, I first looked for peaks in my periodic recorded signal using STFT/spectrogram. From here, I can clearly see ...
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Why does using a log scale ruin (warp) my scaleograms?

I'm trying to make a scaleogram of neural data using the continuous wavelet transform (with Morlet wavelets). As a starting point, I use just a simple sine wave built from two frequencies, 50 and 80 ...
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Good interpolation functions for downscaling magnitude spectrums

I'm trying to downscale a 1D FFT (for displaying an audio spectrogram, like this: My question is, assuming that I have, say, a 512 bands spectrum, what would be the most recommended interpolation ...
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Reconstructing Audio From Spectrogram (Using it as a filter)

Given a spectrogram calculated using the following code: ...
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Artifacts on frequency spectrum

I made a spectograpm in C that takes in a wav file (44.1kHz), converts it to 8bit pcm(can't go higher because of memory constraints) and does 1024 sample FFT on a number of bins, using Welch method. I ...
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How to do high-resolution FFT on just the lower frequencies in a signal?

Description of the data and problem: I have a signal sampled at 1000 Hz. I'm low-pass filtering it at 120 Hz, and want to make spectrograms of the frequencies below this threshold. I'm using the scipy ...
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How to select parameters suitable parameters for a spectrogram

I have a limited background in DSP but I need to generate a spectrogram of an electrocardiography (ECG). I am using the scipy.signal.spectrogram and I need to set ...
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Spectrogram normalizaion to train a Fully Convolutional Model for Audio dereverberation

I'm trying to implement a deep learning based dereverberation algorithm. The network I am using is inspired by the U-net. The idea is to supply the reverberated spectrogram as input and 'clean' it ...
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spectrogram of a (strongly) downsampled file

I downsampled an audio file to a very low sampling rate, 48hz. This is because I stored some information in the file, that are not really audio information but the audio format was convenient to use. ...
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Black dots in spectrogram

Whenever I zoom in on the spectrogram of a recording I made with my phone I see these strange dark dots, unfortunately I cannot try another phone. What is causing them? They seem randomly distributed ...
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Audio Processing - How to create a spectral pitch display?

I want to create an application that analyzes human voice pitch, but spectrograms are very noisy. However, in Adobe Audition, there is a feature called the spectral pitch display, and it successfully ...
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Computable Time-Frequency Distribution without Cross-Terms

Context: I have a single receiver that is receiving multiple signals. Each signal has a few strong harmonics, but I don't know the fundamental frequency. I would like to display them on a spectrogram ...
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scipy.signal.spectrogram() - how to handle gaps in the timeseries data

Looking at the magnitude of variable stars - the dataset is from here: https://dogwood.physics.mcmaster.ca/Cepheid/URL/MW/BD-10d4669.html The magnitude plot: ...
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scipy.signal.spectrogram() with noverlap=nperseg-1, what are the possible side-effects?

I'm using a simulated data set which can be downloaded from the link in the fist paragraph on this page (it's an Excel file): https://www.analyticbridge.datasciencecentral.com/forum/topics/challenge-...
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Can i represent a Time series signal as a spectogram image with desired shape

I am trying to represent sensor data in spectrogram form. The data set consists of multiple 1D time series with a constant frequency of 1024 Hz taken from observations, cut into 1-minute sequences. ...
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Estimating significance in time-frequency spectrograms

I want to investigate the common input of two EMG signals using a wavelet-based approach. To this end, I chose the continuous wavelet transform to approach my research question. In addition, I would ...
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Wrong amplitude in the FFT for 10 seconds measured signal

I measured a signal with the Osziliscope that I generated with a signal generator. The signal is a pure sine wave with a frequency of 1 kHz and a peak amplitude of 2.5 V, I measured the signal for ...
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log(conv) vs conv(log)

Suppose an arbitrary, strictly positive $x[n]$, transformed as $$ x_l[n] = \log(1 + C x[n]) \tag{0} $$ where $C$ is freely chosen. Given the following, where $h[n]$ is a Gaussian lowpass filter (or ...
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Do mel-spectrograms of two audios have linear property?

Suppose I have an audio and some noise, and want to do data augmentation for analysis. Since each audio and noise can have corresponding mel-spectrogram, instead of computing the mel-spectrogram of ...
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Middle C spectrogram in RavenPro

I've been trying to perform a cross-correlation analysis between a Middle C sound (C4) and C5. I'm using the software RavenPro by Cornell to do the analysis. However, I've been unable to see a ...
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What is the advantage of overlapping windows while evaluating Spectrogram?

I've seen many documents that refer to calculate spectrogram through overlapping windows but haven't found clear documents on why this is done and how to calculate the number of points that need to be ...
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Why Matlab Spectrogram of slow and rarely sampled signal shows high frequencies

I have a signal, which was measured for 14.4 minutes (= 864 seconds). There are 192 measurements, so one measurement was done in every 4.5 seconds, which results in a 0.22 Hz sampling frequency if I ...
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How to use tfa.image.sparse_image_warp?

I have the log mel spectrograms of a few audio clips and I am trying to augment the spectrograms using tfa.image.sparse_image_warp so that time warping can be achieved as done in Google's SpecAugment. ...
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How to get rid of noise in audio files?

Is there any method to get rid of noise in wite circles of the spectrogram? I have done the high pass filter for a cut-off frequency of 1 kHz. And I'v also done a adptive noise reduction in adbobe ...
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How to get coordinates(x(time),y(frequency),z(intensity(db))) from spectrogram?

I have created this spectrogram from a wav file. Please have a look: I want to get the x = time, y= frequency, z=intensity(db) of every pixel of the spectrogram. How can I get these coordinates? I am ...
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Why is the mel filter bank used to create a mel spectrogram?

The formula for converting frequencies from Hz to mel scale is as follows: $$2595\log(1+f/700).$$ So why is the mel filter bank used? What is the origin of the mel filter bank?
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STFT with varying window lengths (like the continuous wavelet transform)

I was wondering if it is possible to use windows of varying lengths when making a spectrogram based on the short-time Fourier transform (STFT). That is, for higher frequencies I would use shorter ...
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3 votes
4 answers
2k views

What is really the Mel-filterbank?

After applying STFT to a signal, you typically need to convert the frequencies to the Mel scale. Typically the frequency values range from $0$ to $N/2$, where $N$ is the width of each sliding window. ...
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generating log mel spectrogram using librosa

I have come across 2 different ways of generating log-mel spectrograms for audio files using librosa and I don't know why they differ in the final output, which one is "correct" or how ...
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Why does Matlab spectrogram look stripy when windowed input is zero-padded?

I am working on a little project, and stumpled upon something I cannot understand yet. I am learning cognitive science, and don't have DSP knowledge background, only learning from what I find on the ...
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Tell a recording of Martian wind from a recording of Earth's wind

Perseverance Rover's SuperCam Records Wind on Mars, sol 11 (Credit: NASA/JPL-Caltech/LANL/CNES/CNRS/ISAE-Supaero) How do I interpret an image of a spectrogram of an audio wind signal? (Credit: ...
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How do I interpret an image of a spectrogram of an audio wind signal?

I am running the following code in python to get the spectrogram of a audio signal of wind: ...
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Welch Method FFT Python - Scaling factor?

I've been implementing a Welch method FFT and I am trying to work out the correct scaling factor that should be applied to the output of the function so the PSD is accurate because at the moment it's ...
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2 votes
1 answer
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Spectrogram without using stft

Can I use any kind of transform to make spectrogram, not just stft? Is it possible to get the spectrograms of a signal without using stft? What difference does it make if I calculate the frequency ...
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Stft of sinusoids

I have a sinusoidal signal of 10 minutes. For the first 5 minutes, the signal has a frequency of 100 Hz and for the next 5 minutes, the signal has a frequency of 200 Hz. 1 - If I look at the ...
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Python: How to generate log-frequency spectrogram from an audio?

I want to make a log-frequency spectrogram out of this audio. Later, I need this spectrogram for pitch sequence analysis. This is a sample sequence I want to achieve: ...
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Get Spectrogram from Filtered Power Spectrum

My objective is to get the higher resolution of spectrogram on the high-frequency area (2000 Hz - 5000 Hz) for a section of speech audio. I know that we typically apply Mel-scaled filter bank to get ...
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Confusion about spectrograms: conceptual problem

The following code generates a spectrogram as shown in the image. The matrix s which is the spectrogram is of size 129x40 for a ...
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FM modulation - recovering bits

I'm trying to complete one task: Download some FM modulated signals from page http://www.w1hkj.com/modes/index.htm. Calculate their spectrograms, i.e. short-time Fourier transform. Observe different ...
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How to find peak frequency in an audio frequency spectrum?

I have a audio file consisting of multiple frequencies, I need to find all the frequency peaks in the frequency spectrum after doing FFT. But the issue is how can I be able to set the threshold line ...
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Spectrum of FM signal?

If a carrier ($f_c$) is FM modulated by a single sine wave ($f_m$), its spectrum is composed of frequencies at $f_c + kf_m$ ($k \in \mathbb{Z}$) whose amplitudes are weighted by $J_n(\beta)$, the $k$-...
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revert back to stft from abs and phase

I have the following code on python ...
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1 answer
119 views

Power Spectral Density Reconstruction

I am from an ML background and I am working on MP3 audio reconstruction and I have managed some amount of spectrogram reconstruction but I have noticed that the higher frequency end of the generated ...
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3 answers
4k views

Python audio analysis: which spectrogram should I use and why?

I am doing my final project at university: pitch estimation from song recording using convolutional neural network (CNN). I want to retrieve pitches existed in a song recording. For CNN input, I am ...
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Trade-off in sample-rate & FFT-size & Doppler

I've got a stream of digital IQ samples let's say at $F_s = 1 MSPS$ that consist of a narrowband signal, in awgn. Let's say the signal BW is ~ 100Hz. The narrowband signal's center (or base) frequency ...
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