Questions tagged [frequency]

Frequency in signal processing is the number of cycles (of the signal) per second.

496 questions
Filter by
Sorted by
Tagged with
209 views

Finding the input bit rate of an analogue input

Suppose I have 4 of 300bps synchronous digital input and 1 of analogue input with a bandwidth of 500Hz. The analogue input is sampled at 4bit using PCM. All the channels are multiplexed with TDM. As ...
535 views

Books that explain DSP well to those not directly in engineering?

I do work with computer graphics and am dipping my toes into ray tracing. That field involves a good number of the subjects covered in DSP (Fourier transform, time vs frequency space, etc) but I was ...
3k views

Upsample data using FFTs. How is this exactly done?

I am basing my question on this post here, because I would like additional details on it, as I have not had any success in re-creating it. I would like to simply learn, in no uncertain terms, how to ...
2k views

Are there libraries for extraction of sound wave features?

I am looking help for my project for which I need C++ (or any other language) libraries useful for extraction of sound wave features like frequency, loudness, pitch and orientation. Using these ...
3k views

Why is oversampling helpful to an anti-alias filter?

Why does oversampling make the job of an anti-alias filter easier? I don't understand the intuition on why it becomes helpful. Isn't it economical to just keep the sampling rate at the minimal level,...
366 views

How can I calculate the frequency using different color bands?

Let's say that I have a 1 dimensional signal that has data which comes from one of 2 different spectral bands. The measurements come evenly mixed between the two bands. I'm interested in a method of ...
892 views

differences in fundamental frequency/pitch between music and speech

I am developping a program, that extracts very expressive frames from a video (meaning: frames, which could summarize a video) for a university seminar. One of my ideas was, to analyze the audio data (...
255 views

Procedural wave generation, frequency shift issue

sorry for the long post but I want to try and get all the details in here in hopes it will help. I've been working on building a procedural audio system for use in XNA projects. First this is general ...
458 views

Impulse Response Question

For the differential equation $$\frac{d^2y(t)}{dt^2}+\frac{3dy(t)}{dt} + 2y = x(t),$$ I was able to find the frequency response as $$H(j\omega)= \frac{1}{-\omega^2+3j\omega+2}.$$ However, I am not ...
20k views

Calculating values of frequency bins in Python

I have to use FFT to determine the period of waves inside a signal. After applying FFT on a window of 10000 point from a signal, I get something like this: What I don't understand is that FFT is ...
5k views

FPS to Hertz in a camera

Not sure if this is the proper place to ask this, but I'm sure someone here will know the answer. I have this optical camera (TrackIR 4), which, for what you can see on the table, samples images at a ...
5k views

How to correctly compute the EEG Frequency Bands with Python?

so I am trying to compute the EEG(25 channels, 512 sampling rate, 248832/channel) bands (alpha, beta, gamma, etc.) with Python. I managed to do so by: firstly filtering the signal with a butterworth ...
560 views

Mapping the value of a sample in a 2-D DFT to cycles/pixel

If I have an image and its 2-D DFT of that image, what is the mapping between the value of the DFT at (u,v), and the frequency in the spatial domain in the x and y components, in cycles/pixel? I want ...
165 views

Measuring the “frequency stability” of a signal

I'm thinking about ways to automatically identify and analyze lots of musical instrument samples, and would like to find the part of the sample that's the most stable in frequency, without any ...
744 views

Separating waves of very close wavelengths

I'm new to wave problems, so excuse my simplified words. I have a signal consists of high range of frequencies . I applied a Band-pass filter to this signal and I have been able to separate it to ...
764 views

Removing cyclic noise from signal

I'm using a sensor with output that looks like the following figure. The cyclic noise is common to ask measurements made by the sensor. Is there a way to remove the noise without negatively effecting ...
2k views

Understanding Spatial Frequency of Images (using matlab)

I wish to isolate a crosswalk from its surrounding, and I thought that as crosswalks have a repetitive pattern of thick white stripes, I might be able to isolate them by measuring their frequency ...
2k views

Determine fundamental period from zero crossing signal

I have got a signal which consists of zero crossings over discrete time and I would like to estimate the fundamental frequency (period) from this signal in order to remove noisy samples. The signal ...
3k views

How to compute fundamental frequency from a list of overtones?

Given a list of overtones (F1, F2, F3, etc), how do I compute the fundamental frequency? Can I do something like F2/F1=F1/F0? Is it the correct method to use?
9k views

FFT for a single frequency

I was looking for a more efficient way of finding the magnitude and phase of a signal at a certain frequency without performing an FFT because it produces more information than I need and I came ...
13k views

What does “frequency” mean for various kinds of signals?

I've been involved in Signal processing for quiet a time but I'm still so confused of what frequency could possibly is, as it has different meanings in different scenarios, for example, According to ...
4k views

Adequate representation of frequency domain amplitude/magnitude of FFT of a signal

I'm quite new to the subject and am having fun playing around with the FFT. What I am currently doing is trying to sample an audio signal and display its frequency spectrum at the same time. This ...
11k views

Simple and efficient algorithm to detect frequency and phase of a sine signal

I need an algorithm to detect frequency and phase of a pure sine signal. The frequency of the input signal changes between 0 and 100 Hz. The value of the signal gets captured with a frequency of 20 ...
279 views

Determining the period of a discontinuous function

I'm new to the field of DSP. I'm trying to determine the period and shift of the function. I've tried using FFT, but haven't had much luck. Seems like it should be simple. Signal (pastebin of ...
719 views

Chop out frequencies outside human hearing range

I have a bunch of audio files all sampled at 44100 Hz sample frequency. I am trying to remove all the frequencies which are outside the human hearing range (I use the following as reference: Frequency ...
619 views

Generating inaudible sound waves using MATLAB

I want to generate inaudible sound waves (above 18kHz) with 48kHz sampling rate using MATLAB. Generating a sound wave with 18kHz frequency makes it inaudible. I've inserted the data in the 18kHz ...
3k views

What's the best criterion for determining a frequency peak?

I'm writing an algorithm that analyzes results of discrete Fourier transform (DFT). The algorithm should detect amplitude peaks in predefined ranges of frequencies. This is an example of such a peak: ...
387 views

Why every musical instrument sounds different than any other while listening?

This is soft question.I am not expert in music. We know that English language has 26 letters (which are again grouped into vowels and consonants) , while language of music is same all over the world ...
15k views

Designing High Pass Filter to Remove DC Offset from a Signal

I want to design a high pass filter (f0*S/1+f0*S) in order to remove the dc offset from a signal ? (i.e. how to choose the frequency f0). Thanks, Hacene Ps : the filter is for MATLAB implementation, ...
1k views

Signal Processing/FFT gives very high magnitudes for low frequencies

The script essentially pulls PCM data from the sound card and stores them in a buffer. Then I apply fft and graph it. I am looking through this blog post for some examples and ideas on how to ...
215 views

Fitting fixed number of complex exponentials to complex signal

I have a complex data series, and I would like to fit a fixed number (in this case, two) of complex exponentials of the form $Ae^{jBn}$, where A, B are complex. Not interested in the phase (i.e. arg ...
9k views

Spatial and temporal frequency of a wave

I've sampled a propagating wave so that I know its amplitude at several equidistant points on a line, and at several points in time. That is, I have this discrete function: ...
447 views

What is the role of Freqency in Digital Images [duplicate]

Possible Duplicate: What does frequency domain denote in case of images? If we look deeply into Digital Images they are purely generated by the pixels distributed in rows and coloumn and the ...
350 views

Estimation of the amplitude of a frequency component in a signal

I'm working on a device that produces a signal with sampling rate of 100 kHz. Every 40 ms, I receive 16000 points, from which I have to extract a frequency close to 3.55 kHz. I have developed a method ...
612 views

Spectral Leakage, Phase and other questions about FFT

I'm currently implementing a voice recognition algorithm using FFT and now some questions came up to me: Spectral Leakage: I know what it is, why it appears and how to solve it using a Windowing ...
75 views

Plot spectrum of $X(-k)$

Assume FFT of $x[n]$ is $X(k)$ and I would like to find $X(-k)$. I have implemented two techniques: I am calculating the X(k) = fftshift(fft(x)) and then find <...
1k views

1k views

pitch vs playback rate

Let's say I have an audio sample, whose pitch is known to be C4 (don't wanna go in detail here, let's say I just sampled a tuned piano playing the C4 key). The rules of the game are: I can only ...
83 views

Counting shape changing pattern in signal

I need to count the number of 'patterns per second' in a signal. The problem is that the signal changes 'shape' a lot and unpredictably. It is still easy for a person to see the the pattern, but I don'...
2k views

Comparing Image FFT with Sine wave FFT

So, When we take the FFT of any Composite or Single Sine Wave we get exact frequency on x-axis of the plot. The point where we get the original frequency in FFT is depend upon the Sampling Rate and ...
1k views

Understanding FFT of an Image

I am having trouble identifying the frequency components of an image, Here i simply generated, 256x256 binary-image. ...
181 views

Why is discrete cosine preferred to FFT in neuroimaging GLM

High-pass filtering is often used in neuroimaging data analysis. Commonly, whenever a general linear model is fitted to the data (as for instance in statistic parametric mapping) a number of columns ...
144 views

Codec Output has “Wavy” Amplitude on Chirp Input

I am sending a chirp that sweeps form 20Hz to 500Hz to an audio codec, CS42L52, connected to an MCU, STM32F405, and I am receiving a "wavy" amplitude output. There is no processing on the MCU, I pass ...
2k views

Algorithms for finding fundamental frequency based on ACF result

I am developing a software for fundamental frequency tracking. For this purpose, I have designed a function which calculates autocorrelation over the signal and a second function which, based on ...
187 views

Missing harmonics (power-line)

I have some biomedical signals. If I calculate their magnitude spectrums, I see power-line interference at 50 Hz. I was excepting a harmonic at 100 Hz, but it turns out there is none. However, there ...