Frequency in signal processing is the number of cycles (of the signal) per second.
0
votes
2answers
99 views
Removing noise from audio using Fourier transform in Matlab
I'm trying to remove noise from an audio file. This audio file contains speech as well as constant pink noise. I know that I have to use the Fourier transform to convert to the frequency domain then ...
0
votes
2answers
78 views
Frequency array feed real values FFT
EDIT
The first version of my question has not worked as I expected, so that I will try to be a little bit more specific.
The final goal I am trying to achieve is the generation of a ten minutes time ...
3
votes
1answer
50 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:
...
0
votes
0answers
49 views
How do decide which order my butterworth filter should have?
I have a signal that was recorded with around 300 samples in a second. Now I want to run a low pass and a high pass butterworth filter over it. The frequency for the high pass filter is around 0.05 Hz ...
6
votes
2answers
72 views
Recording and playback of sound, frequencies question
If I record a sound at a rate of 8000 samples per second I know that the highest frequency that can be reproduced from the sound is 4000 Hz. What I want to know is;
If the sound contains ...
3
votes
3answers
82 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?
6
votes
2answers
196 views
How do I determine if a discrete signal is periodic or not?
I want to know how I can determine whether a series of data is periodic or not.
I want to use Fourier transform/series. My data looks either aperiodic
[111100001111000110010101010000101]
or ...
1
vote
2answers
123 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 ...
3
votes
0answers
49 views
Question on spatial sampling for non-linear and/or non-uniform arrays
I am a little confused as to how to compute the nyquist criterion for a sensor array that is not linear, and/or non-uniform. For the linear, uniformly spaced case, the spatial nyquist is delimited by ...
1
vote
1answer
46 views
Frequency vector and fft
I have got a question concerning the definition of the frequency vector for an fft operation.
Generally, I work with a frequency vector, f, with power of 2 ...
0
votes
1answer
69 views
How to calculate the energy levels of frequency intervals of an audio signal?
Using the Fourier transformation I can translate a signal from the time-domain to the frequency-domain. If I divide the frequency axis into intervals, how can I calculate the audios signals energy for ...
1
vote
1answer
41 views
Melodic or tonal pitch contour tracking?
What algorithms or methods can be used for the tracking of audio pitch contours? (Such as in musical vibrato and glissando, or for tonal vowels in languages such as Chinese?). Will a PLL work even ...
1
vote
3answers
83 views
What is the relationship between frequency vector and the peak frequency in FFT?
I am fairly new to both Matlab and FFT. I would like someone to explain to me the relationship between the frequency of the wave being processed, the number of point (usually called NFFT), the Nyquist ...
3
votes
1answer
74 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 ...
2
votes
1answer
46 views
Finding Frequency Differences In Differing Amplitude Signals
I have two audio signals, both with supposedly matching frequencies at each time window. What I would like to do is to verify that the frequencies are identical. However, one was created at a higher ...
2
votes
2answers
88 views
FFT of random binary data
I am trying to make sense of FFTs and binary data.
Say I have a series of random binary data, which is measured with a repetition rate of 400Hz (interval time of 0.0025s). I have a total of 12489 ...
2
votes
0answers
37 views
Varying signal bandwidth with two signal generators
I would like to emulate a signal with bandwidth (like BPSK) for some testing, but the two signal generators I have access to do not have any BPSK options installed. If I know the frequency (2462MHz) ...
0
votes
0answers
29 views
Differentiate between two sounds made by same person
I want to know if i pronounce alphabet "A" then i pronounce alphabet "B" how can i detect the difference between these two sounds. I know a sound is characterized by its frequency and amplitude but ...
1
vote
0answers
26 views
How to convert a sound file to any other data format which can be manipulated
I know this is very basic question and i am new to this site. But can anybody help me with my question. How to convert a sound file to other data format say using some type of transform (FFT or DFT) ...
1
vote
1answer
91 views
Performing classification based on FFT results
It is perhaps important to start with the fact that I am a complete beginner in DSP.
I have got a number of audio recordings (of sampling rate 22 kHz) - of bird songs - which I have been trying to ...
0
votes
0answers
15 views
How do you calculate/compute/determine the spectral coverage of a frequency spectrum?
I'm comparing frequency spectrum of FSK, ASK, QPSK, and MSK. And I'm asked which has the least and greatest spectral coverage. Could someone enlighten me on how to get it?
1
vote
3answers
283 views
FFT Zero Padding - Amplitude Change
I'm just learning about Fourier Transforms and as an input I'm using a WAV file (Matlab) and taking one channel of it and performing a quick Fourier transform. I've zero padded the input, as I've been ...
-2
votes
1answer
53 views
Estimating the frequency of the image [closed]
how to collect data sets from a two dimensional image for estimating the frequency of the image.
how to estimate the frequency of the image.
2
votes
3answers
229 views
Estimating Low Frequencies (including amplitude and phase)
For the past month I've been chasing the DFT/FFT rabbit.
Along the way I've been cut-n-pasting the name of other rabbits to chase later:
Autocorrelation, Phase Vocoder, Parabolic Approximation, ...
2
votes
0answers
50 views
Calculating a filter's attenuation at a certain frequency from the Q-factor
I'm using the Web Audio API to make a graphic EQ with four BiQuad filters; a highpass, two bandpass and a low pass:
You can see each node representing each filter's frequency. It's working nicely ...
2
votes
0answers
90 views
Maximum Frequency deviation in Frequency Modulation
I am writing a script to frequency modulate the stereo audio signal, and later calculating the modulation index wrt time.
As we have to modulate the stereo audio signal, I have to first synthesize ...
0
votes
1answer
39 views
How to calculate the quantum of the difference between two value of clock counter where the values are divided by 64?
I have a counter in my embedded system with f = 64 Mhz.
let's say its read value is $cnt_i$
where $i$ is the index of the time I sampled it.
$$\Delta = cnt_{i+1} ...
2
votes
1answer
102 views
Difference between 'conventional' and 'adaptive' beamformers?
This might be a terminology question but I am not sure.
Basically, what is the difference between conventional beamformers, and adaptive beamformers? I thought that all beamformers were inherently ...
2
votes
2answers
86 views
Setup frequency array properly
I've just stepped into the FFT's world since the last weeks, therefore I still don't have an clear overall idea of how to setup the frequency array.
In case of ...
3
votes
0answers
78 views
Global Transforms besides the DFT?
This is a simple question. Fourier analysis gives us the DFT, which is known as a global transform of a signal. In contrast, the Discrete Wavelet Transform (DWT) has a plethora of wavelets, all of ...
3
votes
1answer
59 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 ...
2
votes
1answer
64 views
Doppler effect on phase
I am struggling to find or derive the relationship between Doppler frequency and the associated phase shift. Let's say I have a signal transmitted at a given frequency $f_c$. I then down convert ...
5
votes
3answers
241 views
Common methods of transmitting digital data through an extremely noisy audio signal?
I am developing software for transmitting data from a computer to a mobile device using audio. Specifically, from the computer's speaker to the device's microphone. (I am developing both the sender ...
3
votes
2answers
60 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 ...
2
votes
2answers
114 views
Extract frequencies from PCM signal
I have an PCM (pulse-code modulation) signal. If I want to work out the frequency of a sample $ x $ long, I count the number of peaks/troughs of the sample, and divide by $ x $. The equivent dB of ...
0
votes
1answer
60 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!) ...
4
votes
1answer
161 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 ...
0
votes
0answers
34 views
are there any tools available that will output audio spectrum as raw data?
Is there an app or script that will output raw text data representing an arbitrary number of bands in the audio spectrum of an input file like a .wav or .mp3 to make the data equivalent of a ...
2
votes
2answers
84 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 ...
1
vote
2answers
98 views
Intuition for how a Fourier transform handles signals where the frequency varies with time?
I created a discrete signal sampled at 44.1kHz that is 330Hz for 1 second, 360Hz for 0.5s, and 390Hz for 0.25s. I did an FFT transformation of this, and got the magnitude graph below:
I don't ...
1
vote
1answer
130 views
Is a DC signal 0 frequency or extremely high?
If I pass a signal with DC component through a Low Pass Filter will the output be without the DC component?
7
votes
1answer
197 views
Ultrasound pulses and reflection problems
I am building a whiteboard to track the position of its pen. I have n ultrasound receivers placed on the periphery of the whiteboard, and an ultrasound emitter in ...
1
vote
3answers
132 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 ...
0
votes
1answer
61 views
Commenting frequency spectrum of a sampled data
the question below asked in my latest signal processing exam. I have no idea about it and i could not find any solution in literature. Could you please help me finding out the answer. Actually i ...
3
votes
1answer
42 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 ...
1
vote
1answer
72 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 ...
4
votes
1answer
140 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 ...
3
votes
1answer
204 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 ...
1
vote
2answers
116 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 ...
4
votes
1answer
145 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 ...
