When we are calling someone from our mobile phone we dial their numbers, each digit of the number sounds different your goal is to identify the key pressed based on the sound.

Question

Saamraaj 2023-10-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2039086-when-we-are-calling-someone-from-our-mobile-phone-we-dial-their-numbers-each-digit-of-the-number-so

回答： Shreshth 2024-1-3

When we are calling someone from our mobile phone we dial their numbers, each digit of the number sounds different your goal is to identify the key pressed based on the sound which you hear.

4 个评论
显示 2更早的评论隐藏 2更早的评论

Star Strider 2023-10-26

Search Answers for DTMF to get an idea of how to approach this.

DGM 2023-10-26

See also:

https://www.mathworks.com/help/signal/ug/dft-estimation-with-the-goertzel-algorithm.html

There are plenty of examples on the FEX of varying complexity and robustness:

https://www.mathworks.com/matlabcentral/fileexchange?q=dtmf

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Shreshth 2024-1-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2039086-when-we-are-calling-someone-from-our-mobile-phone-we-dial-their-numbers-each-digit-of-the-number-so#answer_1382181

在 MATLAB Online 中打开

Hello Saamraaj,

I understand that you are trying to come up with a program that is capable of discerning which digit is being dialled on a phone based on the distinct tone that each number produces.

The problem you've described is related to Dual-Tone Multi-Frequency (DTMF) signalling, which is used for telecommunication signalling over analog telephone lines. When you press a key on a touch-tone telephone, it generates a sound that is a combination of two frequencies: one from a low-frequency group and one from a high-frequency group.

To identify the key pressed based on the sound, you would typically perform the following steps:

Recording or acquiring the sound: Get the audio signal that contains the DTMF tones.
Pre-processing: Filter and normalize the signal if necessary.
Tone detection: Use a method such as the Fast Fourier Transform (FFT) to determine the frequencies present in the sound.
Decoding: Compare the detected frequencies to a known set of DTMF frequencies to determine the key pressed.

Here's an example of how you might implement a simple DTMF decoder in MATLAB:

function key = decode_dtmf(signal, fs)
    % Define the DTMF frequencies for each key
    dtmfFrequencies = {
        % Low frequencies
        [697, 770, 852, 941],
        % High frequencies
        [1209, 1336, 1477, 1633]
    };
    % Define the corresponding keys for each frequency pair
    dtmfKeys = [
        '1', '2', '3', 'A';
        '4', '5', '6', 'B';
        '7', '8', '9', 'C';
        '*', '0', '#', 'D'
    ];
    % Perform FFT on the signal
    N = length(signal);
    Y = fft(signal);
    P2 = abs(Y/N);
    P1 = P2(1:N/2+1);
    P1(2:end-1) = 2*P1(2:end-1);
    f = fs*(0:(N/2))/N;
    % Find the two highest peaks in the FFT
    [peaks, locs] = findpeaks(P1, f, 'SortStr', 'descend', 'NPeaks', 2);
    
    % Extract the two frequencies
    freqs = sort(locs(1:2)); % Sort to ensure low frequency comes first
    % Find the closest DTMF frequencies
    [~, lowFreqIdx] = min(abs(dtmfFrequencies{1} - freqs(1)));
    [~, highFreqIdx] = min(abs(dtmfFrequencies{2} - freqs(2)));
    % Get the corresponding key
    key = dtmfKeys(lowFreqIdx, highFreqIdx);
end

To use this function, you would call it with the audio signal and the sampling frequency as inputs. For example:

% Load or record a DTMF signal
[signal, fs] = audioread('dtmf_tone.wav');
% Decode the DTMF signal to find the key pressed
keyPressed = decode_dtmf(signal, fs);
disp(['The key pressed is: ', keyPressed]);