Load Speech Data

Load an audio data file containing the sentence "Oak is strong, and also gives shade" spoken by a male voice. The signal is sampled at 44.1 kHz.

[y,fs] = audioread('oak.m4a');

% To hear, type soundsc(y,fs)

Define Label

Define a label to attach to the signal. Click Add Definition ▼ on the Labeler tab. Specify the Label Name as Words, select a Label Type of ROI, and enter the Data Type as string.

Create Custom Autolabeling Function

Create a custom function to label the words spoken in the audio file. (Code for the stt function appears later in the example.) See Custom Labeling Functions for more information.

Locate and Identify Spoken Words

Locate and identify the words spoken in the input signal.

Signal Labeler locates and labels the spoken words.

Export Labeled Signal

Export the labeled signal. On the Labeler tab, click Export ▼ and select Labeled Signal Set To File. In the dialog box that appears, give the name Transcription.mat to the labeled signal set and add an optional short description. Click Export.

Go back to the MATLAB® Command Window. Load the labeled signal set. The set has only one member. Get the names of the labels, and use the name to obtain and display the transcribed words.

load Transcription

ln = getLabelNames(transcribedAudio);

v = getLabelValues(transcribedAudio,1,ln)

v=7×2 table
     ROILimits       Value  
    ____________    ________

    0.09    0.56    "oak"   
    0.59    0.97    "is"    
       1    1.78    "strong"
    1.94    2.19    "and"   
    2.22    2.67    "also"  
    2.67    3.22    "gives" 
    3.25    3.91    "shade" 

Change the label values from strings to categories. Use a signalMask object to plot the signal using a different color for each word.

v.Value = categorical(v.Value,v.Value);

msk = signalMask(v,'SampleRate',fs);

s = getSignal(transcribedAudio,1);

plotsigroi(msk,s.y)

stt Function: Locate and Identify Spoken Words

This function uses the IBM Watson Speech API and the Audio Toolbox speech2text extended functionality to extract spoken words from an audio file.

function [labelVals,labelLocs] = stt(x,t,parentLabelVal,parentLabelLoc,varargin)

aspeechObjectIBM = speechClient('IBM','timestamps',true);

fs = 1/(t(2)-t(1));

tixt = speech2text(aspeechObjectIBM,x,fs);

numLabels = numel(tixt.TimeStamps{:});
labelVals = strings(numLabels,1);
labelLocs = zeros(numLabels,2);

for idx = 1:numLabels
    labelVals(idx) = tixt.TimeStamps{:}{idx}{1};
    labelLocs(idx,1) = tixt.TimeStamps{:}{idx}{2};
    labelLocs(idx,2) = tixt.TimeStamps{:}{idx}{3};
end

end