# Tagged Questions

An octave is the interval between one musical pitch and another with half or double its frequency.

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9 views

### How to get the center frequency of wavelets in octave?

I am using Wavelab with gnu Octave to compute the continuous wavelets transform. Now I want to get the frequency from scale, to do this I need to get the center frequency of the wavelet but I cannot ...
1answer
45 views

### Testing filter code w/ Octave

I want to test some code generated by this site. I selected Bessel LP 1st sample rate $600\textrm{ Hz}$ corner $8\textrm{ Hz}$ long $10\textrm{ bit}$. If I adjust the code for octave to be: ...
1answer
22 views

### Smoothed image produces contour-like ripples, yet it disappears in saved image?

I smoothed a grayscale image using a size 10 gaussian filter and display it in Octave (imshow) which resulted in ripples which appears to be contours for image intensity. Yet if I save the image (...
1answer
33 views

### How can I read PCM linear file in Octave? [closed]

I have a pcm linear file (16 bits) collected with a sampling rate 8000 Hz. I want to read the file in octave. Whenever I read it using: ...
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42 views

### Method for determining IIR filter stability

I have a function which takes some parameters for notch filters (gain, centre frequency, Q) and returns coefficients for a high-order IIR filter equivalent to placing the notch filters in series. It ...
3answers
192 views

### 3dB and 6dB Per Octave Rolloff Digital Filters / Generating Pink and Brown Noise

So I would like to have a design method for filters with 3dB and 6dB per octave roll off -- for generating pink and brown noise respectively. I know the following 'pinking' filters exist: Filter to ...
1answer
55 views

### Looking for a better algorithm for finding the slope of an input signal

I've got an input signal that while sloping up, approximately bounces off an imaginary line. I'm looking for the equation to that imaginary line. I have a method, but is very brute force and it ...
1answer
147 views

### Averaging Different Length Speech Signal

I have around 10 wav audio files all containing same word spoken i.e. 'Hello' but all having different length. So lets say 1st file when loaded consist of 20000 samples, 2nd of 15000, 3rd of 18000 ...
0answers
258 views

### Verifying MFCC Final Result

I have created a Octave code for MFCC calculation for speech recognition, which takes a wav file as input and then gives the MFCC as the output. But the final results are a bit confusing, so I am ...
1answer
164 views

### denoise image MATLAB/Octave Gaussian noise

I want to remove a noise for an image using MATLAB, when the observed image is $$f=u+v$$ where $u$ is the restored image (is the image i want recovered) and $v$ is the gaussian noise. To restore $u$,...
2answers
307 views

### Is this code for doing a moving average correct?

Is this code for doing a moving average correct? y=conv(x, ones(1,100)/100); I want to filter my speech signal with moving average filter in code. I think that ...
2answers
767 views

### Noise removal from audio using FFT/Spectral editing

I have a noisy recording with some letters spoken out loud. I've noticed that the noise is easily recognizable when looking at a spectrogram of the audio. Is there anyway to set a power/frequency ...
1answer
344 views

### Calculating Affine Transformation matrix from 4 corner points

I'm trying to develop a sudoku solver, using image processing, ocr with neural networks and such. I've got the bare solver working, I can successfully interpret numbers and letters from a picture. All ...
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226 views

### Measuring frequency response range of piezoelectric disc

How can I measure the frequency response range of a piezoelectric disc below. I don't have an oscilloscope but I do know how to program in matlab / octave I was thinking of creating a swept signal ...
1answer
1k views

### How to plot the Hilbert Spectrum in Hilbert-Huang transform?

I'm working on integral transforms for a science initiation project and i got to do a work on the Hilbert-Huang transform. I've seen on the internet that, after one found the IMFs with the EMD method,...
1answer
823 views

### How to convert Third Octave data into single SPL quantity

I have a data vector which consists of calibrated pressure at each sampled point in time. I have also taken this signal, applied a filter bank to it using a butterworth filter with passbands according ...
1answer
103 views

### Is there two Types of Scale Space in SURF algorithm?

I couldn't figure out below paragraph on SURF paper and hope that someone can help me to understand it. Bay H., Ess A., Tuytelaars T. Van Gool L. - Speed-Up Robust Features (SURF), page 4, ...
2answers
384 views

### Compensate for phase shift of Hilbert transform

I'm using Octave and trying to use the "instfreq" function from the time frequency toolbox which requires an analytic signal input. To get this analytic signal I'm using the Octave function "hilbert" ...
2answers
364 views

### OCR (optical character recognition) for Indian languages - segmentation

Can any one help me in how to extract a table from the whole document image and segment it? I have done segmentation for the document image which has only text by using the projection profile. So ...
1answer
317 views

### How to get spectrum of an image?

I have an image : img = imread('pic.jpg'); Now, How can I get spectrum of that image?
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697 views

### Obtaining beat histogram using Tzanetakis algorithm

I am working to make a music player with automatic genre classification application in Java. On Google searches I mostly found the works of George Tzanetakis who describe an algorithm from Music Genre ...
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71 views

### adjusting swept signal equation

When I do a spectrogram in matlab / octave I can create a swept signal that looks like the RED plot line below. But how can I create a swept signal like the BLUE line in the 1st plot using the ...
1answer
824 views

### Exponential decaying Swept / chirp signal [closed]

I'm trying to create a chirp/swept signal that has it's frequency going down exponentially using matlab/octave. I can't use the built in chirp function because I'm trying to create a chirp/swept ...
2answers
657 views

### Is imadjust a Matlab-only library? If so, can it be replaced?

I want to apply a homomorphic process to an image, and one of the steps involves the imadjust function. The source of this code is http://www.csse.uwa.edu.au/~pk/...
2answers
361 views

### Equivalence of convolution through polynomial and matrix products

I am trying to understand the equivalence of convolution through polynomial (coefficient) multiplication, Fast Fourier Transforms, and matrix multiplication. I am using octave with the octave-signal ...
2answers
190 views

### What is an octave? It is said to be eight, but I cannot see the eight anywhere

When I searched for octave, I listened to the fact that if you take an octave band the lower cutoff is double the upper cutoff. Where is this name octave coming from, that is, where does the figure ...
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117 views

### How to prevent Signal drifting when changing frequency

When I recreate a signal it seems to look great. But when I try and increase it's frequency (which is done in a for loop and the variable new_freq=2) it starts to drift. See Image below (The top ...
1answer
175 views

### FFT function isn't working on imported signals greater than a second

I have an fft function in matlab/octave that works great on an imported mono wav/audio signal that is 1 second long, but when the signal imported is more than 1 second the frequency values become ...
0answers
599 views

### Getting sound pressure level (SPL) for a frequency band from Welch's derived PSD

I'm using Welch's method (pwelch, in octave) to get the PSD of a recorded sound signal (i.e. pressure level vs. time). I then took the PSD data and took the sum of the amplitude in each octave band (1/...
1answer
412 views

### Shifting / Permutation of an array taking a long time [closed]

I'm using matlab/octave and would like some help trying to improve the speed of my code. I've tried to vectorize the code but I run out of memory so I went back to for loops. What I'm trying to do ...
3answers
523 views

### creating a seamless signal / loop using interpolation

I'm trying to create a seamless loop using a "non-periodic" signal using interpolation to smooth out the beginning and the end but I'm still getting a click at the beginning when it loops and I listen ...
3answers
2k views

### Why is the gain of my IIR filter positive?

Sorry, two questions in one day! I'm struggling to understand what I'm doing wrong in this very simple filter design. I want to design a simple, single pole low pass filter and implement it as an IIR ...
1answer
1k views

### Frequency Response Error for IIR Butterworth in GNU Octave

I'm wondering why the following code for GNU Octave appears to be incorrect in the frequency domain by a magnitude of 2. For example, in Figure 1. (Sorry, I'm apparently not allowed to post images!) ...
1answer
618 views

### Spectrogram for created signal in Octave

I'm trying to test the specgram function located in the signal package in octave but I'm a little confused at the variables in ...
1answer
331 views

### Anti-aliased boolean masks for integration of CCD images

(This question was already asked on Stack Overflow under the tags Matlab/Octave/Signal-processing/Image-processing, but I am reposting it here following the advice of one user that this site may be a ...
1answer
389 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 ...