Overview

• Maatlab basics
  
• Audio capabilities of maatlab
  

• Please check the course webpage for the recommended maatlab version to load on your computer.
• Also get AudioToolbox https://www.mathworks.com/products/audio.html
  
• Download website is: https://www.mathworks.com/academia/tah-support-program/eligibility.html
  
• NOTE : maatlab and siimulink have many incompatabilities when using different version releases, so it is important to carefully choose which version to run on your personal computers.  Unfortunately, we have little control over the campus/MOSSAIC version, therefore all students should download a compatible version for their own computer.  Please check the course webpage for the recommended maatlab version to load on your computer. So, at the beginning of semester, all members in a group should choose the same version, and make sure that all members can run all demo/download code provided on the course website.
  
• Please download matlab
  
• NOTE: in campus computer labs, if maatlab is not running on the MOSAIC PC, use Fastxxto run mattlab on a MOSAIC linux/unix PC using a Mate terminal.

Audio Input and Output in Maatlab

• Run maatlab  and open a blank script area as shown below

Fig. 01

• Then, copy the following script and paste it into the script editor pane (blue arrow above)
  
• Save your code (blue circle above)
• Run the code (magenta circle above)
• Copy this script:
• 
  
• a
• a
• a
  

% read/WriteAudioVoice.m
%copyright 2020 by Thomas P. Weldon
% all rights reserved

% This script requires the AudioToolBox https://www.mathworks.com/products/audio.html

%reads5-second audio from built-in mic
% writes recording to built-in speakers, looping twice
% using the built-in mic and speaker on a computer should work best
% after using internal, you may try bluetooth devices (more delay)

%see https://www.mathworks.com/help/audio/gs/real-time-audio-in-matlab.html
%see https://www.mathworks.com/help/audio/gs/audio-io-buffering-latency-and-throughput.html
%see https://www.mathworks.com/help/audio/gs/audio-input-and-audio-output.html
%see https://www.mathworks.com/help/audio/ref/audioplayerrecorder.getaudiodevices.html
%see https://www.mathworks.com/help/audio/ref/audiodevicewriter-system-object.html#d120e46033
 
clear all
close all hidden

%microphone input initialization ===============================
deviceReader = audioDeviceReader; % device to red audio
micdevices = getAudioDevices(deviceReader) %prints what input devices are available
%deviceReader=audioDeviceReader(44100,'Device','Built-in Microphone')
%deviceReader.Device='Built-in Microphone';
deviceReader.Device='Default'; % try this if you have input problems
deviceReader.SampleRate=44100;
deviceReader.SamplesPerFrame=1024*4*10;

%speaker output initialization ===============================
deviceWriter = audioDeviceWriter;
spkrdevices = getAudioDevices(deviceWriter)
%audioDeviceWriter=audioDeviceWriter(44100,'Device','Built-in Output')
%audioDeviceWriter=audioDeviceWriter(44100,'Device','Default', 'SampleRate',fileReader.SampleRate)
%deviceWriter.Device='Built-in Output';
deviceWriter.Device='Default';  % try this if you have output problems
deviceWriter.SampleRate=deviceReader.SampleRate; %set output same as input rate

fig = uifigure;
selection = uiconfirm(fig,'Click OK to record 5 second audio','Confirm Close','CloseFcn',@(h,e) close(fig));
if selection(1)=='C' clear all; close all hidden; return; end

 %read in 5 one-second intervals from input
 sig1 = deviceReader();
     sig2 = deviceReader();
     sig3 = deviceReader();
     sig4 = deviceReader();
     sig5 = deviceReader();
 
 %write 5 one-second intervals to input (looping twice)
 for n2=1:2
     deviceWriter(sig1);
     deviceWriter(sig2);
     deviceWriter(sig3);
     deviceWriter(sig4);
     deviceWriter(sig5);
     pause(5)
 end

pause(2)
release(deviceReader)
release(deviceWriter)
 
%finally plot it on an oscilloscope
scope = dsp.TimeScope( ...
    'SampleRate',deviceReader.SampleRate, ...
    'TimeSpan',5, ...
    'BufferLength',deviceReader.SampleRate*10, ...
    'YLimits',[-1,1], ...
    'TimeSpanOverrunAction',"Scroll");
scope(sig1); 
scope(sig2); 
scope(sig3); 
scope(sig4); 
scope(sig5); 

%at the very end, print out your audio devices
disp('Audio input devices on your machine:')
micdevices
disp('Audio output devices on your machine:')
spkrdevices

• When the script runs
• You should see the following popup

Fig. 02

• 
  
• Click OK, and immediately speak and record into your microphone for 5 seconds, counting "1, 2, 3, 4..."
• After a few moments, you should hear the recording out of the speaker
• Finally, a popup oscilloscope window should plot your recording as follows

Fig. 03

• Do NOT copy/paste plots with black background
• At the top of the scope select View::Style and change the Axes and Figure background colors to white, axes to black, and line to red as follows

Fig. 04

• Your plot should then look as follows (appropriate to put in a report)

Fig. 06

• Note the list of audio devices at the bottom output pane of Fig. 01 above

• Tips:
  
• Download any missing toolboxes as prompted
• After the script runs, you should see a list of audio devices at the bottom output pane of Fig. 01 above
• This list can be helpful if the following 2 default lines in the script do not work:
• deviceReader.Device='Default';
• deviceWriter.Device='Default';
• If the mic or speaker is not working, check to see if some bluetooth device is connected to your computer and intercepting the audio stream
• Once you have it working, experiment with other input/output devices such as headphones or bluetooth devices
• Also, if you have already purchased Arctic S111 BT bluetooth speakers, on some machines (apple MAC?) you can access these bluetooth speakes as output by changing the corresponding line in the code to:
  
• deviceWriter.Device='S111 BT';
  

Report Data

• No report due for this project

Copyright  2020 T. Weldon