Signal Processing

Questions tagged [spectrogram]

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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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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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63 views

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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14 views

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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71 views

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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1answer
52 views

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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2answers
30 views

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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84 views

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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1answer
55 views

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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29 views

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: enter image description here I want to get the x = time, y= frequency, z=intensity(db) of every pixel of the spectrogram. How can ...
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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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180 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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117 views

Time-Frequency analysis of IQ data in MatLab

I am new to signals processing, and am trying to match the information I'm getting out of MatLab to that taken from a commercial spectral visualization/playback tool. That is, I know what my data ...
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What is the unit of the color axis on a Matlab spectrogram, and bandpower?

I am new to signal processing, but successfully made a spectrogram with Matlab. It is nice and working, showing the expected output on the graph, but I just cannot understand what the numbers mean on ...
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204 views

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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159 views

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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33 views

Audio-Processing for DeepSpeech model

I try to understand audio signal processing from Deep Speech: Scaling up end-to-end speech recognition paper. Quote: Since the Switchboard and Fisher corpora are distributed at a sample rate of 8kHz, ...
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1answer
44 views

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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34 views

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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Stockwell S-Transform and multitapering

I want to estimate just the spectral amplitudes at different time points using S-transform given a noisy signal. Would I benefit (in terms of noise reduction) from an approach used in multi taper ...
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341 views

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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Use of spectrograms in using deep learning on EEG related problems

I am currently working on a classification problem related to EEG signals. My professor asked me to convert those signals into their spectrograms and try various convolutional neural networks on them. ...
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31 views

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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43 views

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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49 views

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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101 views

How to determine number of filters in filter bank based on spectrogram of audio signal?

I want to do an analysis and than synthesis of audio signal, which is audio of vowel 'a', using Matlab. For this I need to use filter bank(array of band-pass filters). I have drawn four different ...
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1answer
222 views

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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441 views

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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How to apply audio superposition in mel spectrogram domain

Very rusty physicist here. I have two audio spectrograms and I want to work out how to calculate the spectrogram of the superposition of the original waveforms (without having access to the original ...
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1answer
153 views

revert back to stft from abs and phase

I have the following code on python ...
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1answer
67 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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3answers
3k 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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68 views

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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51 views

Understanding CQT (Constant-Q Transformation) parameters for piano AMR (automatic music recognition) with Librosa Library

I am doing an automatic music recognition project with a deep learning model. For my data preprocessing, I am trying to calculate the Constant Q Transform for Polyphonic 88-key piano audio using ...
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2answers
88 views

Questions about MP3 bitrate conversions

I was trying to analyse the lossy compression of MP3 audio files through their Spectrograms and the results were something like this (where the upper is 80Kbps and lower is 128Kbps). It is obvious ...
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60 views

Plot Spectrogram and FFT plots from samples collected by Atheros AR9271

I'm entering the world of signal processing, and as one of my first projects I've decided to plot a spectrogram and FFT Plot. The samples comes from an Atheros AR9271. More details can be found here: ...
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42 views

How to efficiently apply spectrum sensing algorithm

Lets assume 1 signal (lets call it PPG) that is composed "mostly" of 3 different main frequencies components ($f_1, f_2, f_3$) and their harmonics. Now let's assume we have 16 copies of this ...
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96 views

Determining statistically the bandwidth of a signal from a spectrogram

My question is how to determine the parameters of a signal from a spectrogram statistically. The most important parameters that I am looking for are the lower and higher frequencies of the signal. I ...
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1answer
125 views

How does modulation frequency appear in the modulation spectra?

I'm trying to familiarise myself with the concept of modulation spectra that I met in this work. My main question appears in the title: how does the modulation frequency appear in the modulation ...
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32 views

How can I perform sound classification based on spectrograms and waveforms?

I noticed that almost all machine learning enabled sound classification approaches use spectrograms or MFCCs as input for feature extraction. I am new to the area and would like to know if we can also ...
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1answer
56 views

spectrogram of a leak in a water pipe

I'm doing a work on the acoustic emission of a leak. I am using a 1.80 m cylindrical tube with water, and the leak is simulated by means of a tap that opens after I have applied negative pressure ...

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