I'm looking for an Objective-C class that allows me to get the frequency of a live input sound on the iPhone. Didn't find anything useful.
Before you ask: the frequency will not change for 0.1 seconds.
Thanks for answers,
Christian
Following is the library used to fid the frequency..
A lib to find the frequency https://github.com/jkells/sc_listener
A example using the above library https://github.com/jkells/sc_listener_sample
Hope it helps some once..
Do you mean frequency or pitch ? If it's just a pure sinusoid and you want the frequency then you can just measure the time between zero crossings (crude) or use an FFT to get the power spectrum and then find the peak (more complex, more reliable).
Related
I want to detect speech signals pitch frequency using autocorrelation algorithm. I have a MATLAB code but the results are wrong. I would be grateful if you could solve the mistake in my code.
[y,Fs]=audioread('Sample1.wav');
y=y(:,1);
auto_corr_y=xcorr(y);
subplot(2,1,1);plot(y)
subplot(2,1,2);plot(auto_corr_y)
[pks,locs] = findpeaks(auto_corr_y);
[mm,peak1_ind]=max(pks);
period=locs(peak1_ind+1)-locs(peak1_ind);
pitch_Hz=Fs/period
Thank you for your help in this matter.
Seems, your code do not works because the Sample1.wav must contains only the short quazi-periodic part of the vocalized record. Also note, the pitch frequency is not the constant over time, so your estimation must takes this into account.
If you just want to estimate the frequency, you can take the RAPT method from the Speech Filling System (see the sfs_rapt.m wrapper for Windows).
I have data from an accelerometer and made a graph of acceleration(y-axis) and time (x-axis). The frequency rate of the sensor is arround 100 samples per second. but there is no equally spaced time (for example it goes from 10.046,10.047,10.163 etc) the pace is not const. And there is no function of the signal i get. I need to find the frequency of the signal and made a graph of frequency(Hz x-axis) and acceleration (y-axis). but i don't know which code of FFT suits my case. (sorry for bad english)
Any help would be greatly appreciated
For an FFT to work you will need to reconstruct the signal you have with with a regular interval. There are two ways you can do this:
Interpolate the data you already have to make an accurate guess at where the signal would be at a regular interval. However, this FFT may contain significant inaccuracies.
OR
Adjust the device reading from the accelerometer incorporate an accurate timer such that results are always transmitted at regular intervals. This is what I would recommend.
I want to know the frequency of data. I had a little bit idea that it can be done using FFT, but I am not sure how to do it. Once I passed the entire data to FFT, then it is giving me 2 peaks, but how can I get the frequency?
Thanks a lot in advance.
Have a look at this page for an explanation on how to calculate it:
FFT Fundamentals
Please also check this answer (it's C# code but I think you can easily understand it)
How do I obtain the frequencies of each value in an FFT?
And finally have a look at this one, it uses DFT instead of FFT:
Determining the magnitude of a certain frequency on the iPhone
I also found this implementation that you can use in Objective-C:
A lib to find the frequency https://github.com/jkells/sc_listener
A example using the above library https://github.com/jkells/sc_listener_sample
Regards
An FFT will give you the frequency of all the sinusoidal components of a signal. If instead you want just the frequency of the periodicity of common waveforms (more interesting sounding and looking that a plain sinewave) such as produced by speech and music, then you may want to use a pitch detection/estimation algorithm instead of just an FFT peak.
I have just recorded a tiny section of audio in MatLab using the >> x = wavrecord( 2*fs, fs, ‘double’); command.
So far I have figured out how to playback the audio using soundsc(x, fs); and to plot to a graph using plot(x).
Here is a zoomed in screen capture of my wave:
Does the x-axis display the duration in milliseconds and the y-axis display the amplitude?
I think I may have switched off the axis names by accident.
I need to confirm this before i try to calculate the Fundamental Period and Fundamental Frequency of the wave.
If I've guessed my axis correct, am I right in thinking the fundamental period is the amount of time it takes for one periodic wave to repeat itself, making it (T)? So in this case approximately 0.0050 seconds?
And, the fundamental frequency is f0 = 1/T = 1/0.0050?
I have been playing around all day and reading so much. I hope i havent confused myself and just embarrassed myself on this site. Thanks.
Your x-axis is just sample number. This would go from 1 to the number of samples your sound recording contains. The sample time which is the time period between two samples is 1/fs. fs is your sampling frequency. So the time period for 50 samples would be 50/fs.
For most waveforms you cannot find Fundamental period easily by looking at it. As #duffymo mentions you need to compute FFT or PSD and then find the location of your first peak which is not DC. This would be your fundamental frequency.
This time trace looks pretty noise to me. It's not "frequency"; it's "frequencies".
If you do an FFT on this, you'll find that there are lots of frequencies involved. You may be able to reproduce the main signal with a smaller number of harmonics, but I doubt that it'll be just one.
I am new to iphone development.I am doing research on voice recording in iphone .I have downloaded the "speak here " sample program from Apple.I want to determine the frequency of my voice that is recorded in iphone.Please guide me .Please help me out.Thanks.
In the context of processing human speech, there's really no such thing as "the" frequency.
The signal will be a mix of many different frequencies, so it might be more fruitful to think in terms of a spectrum, rather than a single frequency. Even if you're talking about
a sustained musical note with a fixed pitch, there will be plenty of overtones and harmonics present, in addition to the fundamental frequency of the note. And for actual speech,
the frequency spectrum will change drastically even within a short clip, due to the different tonal characteristics of vowels and consonants.
With that said, it does make some sense to consider the peak frequency of a voice recording.
You could calculate the Fast Fourier Transform of your voice clip, then find the frequency
bin with the largest response. You may also be interested in the concept of a spectrogram, which represents how the audio spectrum of a signal varies over time.
Use Audacity. Take a small recording of typical speech, and cut it down to one wavelength, from one peak to another peak. Subtract the two times, and divide 1 by that number and you'll get the frequency of your wave in Hz.
Example:
In my audio clip, my waveform runs from 0.0760 to 0.0803 seconds.
0.0803-0.0760 = 0.0043
1/0.0043 = 232.558 Hz, my typical speech frequency
This might give you a good basis to create an analyzer. You'd need to detect the peaks, and time between the peaks of the wave and do an average calculation of the result.
You'll need to use Apple's Accelerate framework to take an FFT of the relevant audio. The FFT will convert the audio in the time domain to the frequency domain. The Accelerate framework supports the FFT and will allow you to do frequency analysis in real-time.