# Questions tagged [frequency]

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

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### 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 ...
114 views

### Establishing the function of a decaying signal

I have a set of samples from a signal. The signal is erratic in behaviour at the beginning but then it settles down and oscillates around the value of 100 (the frequency of oscillation is not ...
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 ...
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 ...
469 views

### Applying Window Function to Low Frequency Signals

I'm computing 1 sec. hanning windows from a signal that has a variable frequency between 1-4Hz. My first impression is that data loss caused by the distortion due to the window function is greater ...
6k views

### How is it possible to Filter out a person's voice out of 100 of other voices?

So, I've just learned that the human voice is not a single sine wave its a bunch of unlimited Sine waves each having a different frequencies, According to Wikipedia, The voice consists of sound ...
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 ...
14k views

### Most efficient way to extract frequency components of audio signal with near-human accuracy in real time

I'm trying to work out how (if possible) to extract the frequency components of an arbitrary audio sample (typically music) in an FFT-like manner, but in my research on the FFT algorithm, I'm learning ...
779 views

### Fractional Frequency and negative Frequencies

So, when we Sampled any signal at the rate lower than Nyquist Frequency we get aliasing, for instance, If the frequency of Cosine wave is 5Hertz and I had to make 5cycles in a second and if the ...
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 ...
26k views

### Amplitude of the Signal in Frequency Domain different from Time Domain

How does the Amplitude of the Signal is changed when taking the FFT of a Signal, Have a look, The amplitude had changed from 2 to 30, and Here is my code for generating the above output, ...
172 views

### Time Period of one Cycle is way too large

I am calculating Time period of Sine/Cos Wave with different frequencies while keeping the Sampling Frequency at 1MHz and plotting it, but in some cases the value of time period is too big, have a ...
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. ...
62k views

### time in Sine Wave equation

According to Wikipedia, The sine wave or sinusoid is a mathematical function that describes a smooth repetitive oscillation. The formula for the Sine wave is, A = Amplitude of the Wave ω = the ...
727 views

### What features describe audio signals? (Besides frequency and amplitude)

I recorded sounds with a microphone and I try to distinguish them in my Java program. The frequency works quite good, but if I look at the fourier transforms it seems like there should be more ...
283 views

### Frequency/harmonic analysis of accents

I am looking to find out how accents could/would be detected by a programme, I haven’t as of yet undergone an experiment into detecting or observing anything noticeable about recorded accents. I am ...
449 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 ...
752 views

### Detect presence of a specific frequency (or lack thereof)

I know very little DSP beyond an intro undergrad course. I was looking to write a C algorithm that takes ADC samples and determines if a specific frequency is present (in the range of 100KHz); not ...
169 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 ...
14k views

### How to make frequency axis for even and odd FFT length?

Can I get help on how to make frequency axis going from negative frequency to positive frequency, (in Hertz), that will be the x-axis in an FFT result, but given either an even length FFT, or odd ...
119 views

In the documentation for the [XAudio2 filter parameters] it mentions Filter radian frequency calculated as (2*sin(pi*(desired filter cutoff frequency)/sampleRate)) ...
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### How do optical illusions work (photo mosaic) from a signal processing perspective?

Hello fellow investigators I have two question about optical illusions 1) A photo mosaic is something like this: What are the signal processing principles behind our eye merging the many tiny ...
1k views

### Signal matching: How to quantify the difference between two signals of varying frequency

I have two waves, and I would like to quantify the difference between them. They are exponential sine waves where the frequency decreases with time. I'm interested in the difference in decay ...
15k views

### What is the bandwidth of a (real) sinusoidal tone, and pulse?

I would like to know how to go about calculating the bandwidth of: A constant (real) sinusoidal tone A (real) sinusoidal pulse. The question is as simple as that, but I am having a hard time with ...
772 views

### How to Shift Carrier Frequency in QAM Signal?

If I wanted to apply a 100Hz frequency shift to a QAM signal with a 500MHz carrier frequency, I would Demodulate it at the carrier frequency Apply a frequency shift to the original signal Modulate it ...
897 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 (...
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### Why can Quadrature Demodulation demod a Frequency Modulated Signal?

I use a Quadrature Demodulator in my SDR application, which is defined as: $\angle (S_n, S_{n+1})=arctan(S_{n+1}*\overline{S_{n}})$ So practically its amplitude is the angle between two Samples $S_n$...
10k views

### How do I create a frequency vs time plot?

I'm a chemical engineer, not an EE, so this is a bit difficult. I'm trying to figure out how to take amplitude vs time data and transform it into frequency vs time. My first instinct is to slice my ...
6k views

### Determining Frequency and Period of a wave

I'm gathering temperature data from a refrigerator. The data looks like a wave. I would like to determine the period and frequency of the wave (so that I can measure if modifications to the ...
56k views

### Why Carrier signal can't have frequency less than Message signal

I know that why we use Carrier of high frequency to send message signal over a long distance, when the frequency is low , energy will be obviously low. To increase the energy of the signal we need to ...
1k views

### On using eigenvectors to estimate a signals' fundamental frequency, via MUSIC

Context: (Disclaimer: This is NOT a comm problem). I am trying to estimate the fundamental frequency of a real, periodic signal. This signal, was constructed by match filtering a raw signal, to that ...
17k views

### Why are sidebands generated in AM and FM?

When the signal is modulated onto the carrier in the electromagnetic spectrum, that signal occupies the small portion of the spectrum surrounding the carrier frequency. It also cause sidebands to be ...
11k views

### If Digital Signal has frequency components then why we don't use it

As we know there are two kinds of signals: analog signals and digital signals. And there are two common techniques for multiplexing the signals: Time Division Multiplexing (TDM) and Frequency ...
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### 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 ...
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### I need advice about how to make an audio frequency analyzer

I just need some clarification of some very basic aspects of creating a frequency analyzer. I am writing a c++ program, so far it is just a media player, with a custom explorer. You can make ...
433 views

### Extraction of non-sinusiodal repetition rates

I have an auto-correlation function that was generated from a signal, and I am trying to extract its 'repetition rate' in order to calculate the dominant frequency of the pulse, but I am not exactly ...
2k views

### period of this signal

it could be a donkey question but I'm a little confused. I have this signal $w(t)=sin({\pi}0.1f)$. I have to calculate the period of this signal. $w(t)=sin(2{\pi}\frac{1}{20}f)$ the period of this ...
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### Why does a wave continuously decreasing in frequency start increasing its frequency past the half of its length?

I'm trying to programmatically generate a wave (sine or square) with a continuously decreasing frequency. To do so, I simply multiply the starting frequency for a decreasing value, that linearly goes ...
19k views

### How to shift the frequency spectrum?

Lets say we have a spectrum ranging from -X MHz to +X MHz. I would need to correct the frequency error in the spectrum by shifting the zero component to the middle (0 Hz). If the output (the ...
2k views

### Efficient frequency offset estimation of known signals

Let's say that my receiver will be receiving known data signals that range from the very simple (tone) to the complex (known data sequence that is modulated (PSK/QAM/OFDM/etc.)). What are the most ...
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: ...
259 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 ...
1k views

### Does down-mixing a signal before taking the fourier transform aid in signal detection?

Let us assume that we have a narrowband signal $s[n]$, at frequency $f_1$, and let us further assume that this $f_1$ is just below $\frac{f_s}{2}$, where $f_s$ is the sampling rate. Furthermore, let ...
1k views

### Noisy Frequency Estimation using Hilbert Transform

I'm looking for a way to estimate instantenous frequency with low time-variation. The following MATLAB function (save as test_fest.m) does this using the Hilbert ...
25k views

### what is the gabor filter, and what are its main uses

I'm doing a research on Gabor filter, but when I Googled it, I had very long and complicated articles. Can anyone help me to find a simple explanation about it, or recommend a website or article to ...
239 views

### Modeling spring oscilliations with electric noise (50 hz)

I have Analog to Digital converter from which I get data of measurements of 1kg load. The aim is to model the simple spring-damper system, so that after entering correct initial data (x[0] = a, x'[0] =...
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### Is there an algorithm for finding a frequency without DFT or FFT?

I was looking in the Android app store for a guitar tuner. I found a tuner app that claimed it was faster than other apps. It claimed it could find the frequency without using the DFT (I wish I still ...
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### Find h[n] using DTFT properties

Using the DTFT property, find h[n] of a system where: Is it an FIR or IIR system?