Click here to Skip to main content
Click here to Skip to main content

Sound Activated Recorder with Spectrogram in C#

By , 27 Jan 2008
Rate this:
Please Sign up or sign in to vote.
SoundCatcher

Introduction

This project demonstrates an implementation of the waterfall spectrogram and use of statistical data to trigger events in near real-time. This code is an elaboration of my previous submission (SoundViewer). This demonstration utilizes the Wave classes developed by Ianier Munoz.

Using the Code

Audio is supplied by the default input device which is typically the microphone. Events are triggered when audio amplitude exceeds the desired threshold value, which can be set under Options on the menu bar. To make this more useful, I've added functionality to save the stream to disk which results in a nice sound activated recorder.

Points of Interest

In order to draw the spectrogram fast enough to allow for near real-time operation, I needed to write directly to memory using unsafe code.

// lock image
PixelFormat format = canvas.PixelFormat;
BitmapData data = 
    canvas.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadOnly, format);
int stride = data.Stride;
int offset = stride - width * 4;

// draw image
try
{
  unsafe
  {
    byte* pixel = (byte*)data.Scan0.ToPointer();
    // for each column
    for (int y = 0; y <= height; y++)
    {
      if (y < _fftLeftSpect.Count)
      {
        // for each row
        for (int x = 0; x < width; x++, pixel += 4)
        {
          double amplitude = ((double[])_fftLeftSpect[_fftLeftSpect.Count - y - 1])
                [(int)(((double)(_fftLeft.Length) / (double)(width)) * x)];
          double color = GetColor(min, max, range, amplitude);
          pixel[0] = (byte)0;
          pixel[1] = (byte)color;
          pixel[2] = (byte)0;
          pixel[3] = (byte)255;
        }
        pixel += offset;
      }
    }
  }
}
catch (Exception ex)
{
  Console.WriteLine(ex.ToString());
}

// unlock image
canvas.UnlockBits(data);

I noticed that the results vary wildly depending on the hardware and associated drivers being used.

Some things I'd like to experiment with further when I get the time:

  1. Use of frequency domain to produce "motion" detector equivalent
  2. Use of spectrogram in sound identification
  3. Improving performance/robustness

History

  • 01/16/2008: Created

License

This article, along with any associated source code and files, is licensed under The GNU General Public License (GPLv3)

About the Author

Jeff Morton
Systems / Hardware Administrator
United States United States
No Biography provided

Comments and Discussions

 
GeneralRe: Excellent piece of work Jeff PinmemberJeff Morton5-Jul-09 5:46 
GeneralThrows exception when using Freq &lt; 11025 Hz Pinmemberk^s10-Jun-09 7:07 
QuestionHow do I get it to work? PinmemberMaiden Computer Company22-Apr-09 10:48 
AnswerRe: How do I get it to work? PinmemberJeff Morton22-Apr-09 10:51 
QuestionError in Frequency domain? PinmemberElysium8-Mar-09 11:17 
AnswerRe: Error in Frequency domain? PinmemberJeff Morton8-Mar-09 11:41 
GeneralRe: Error in Frequency domain? PinmemberElysium8-Mar-09 22:02 
QuestionQuestion on how to get the frequencies Pinmemberkyanmark_johnwill2-Mar-09 13:52 
Hi, Mr. Morton!
 
My groupmates and I have a project in which we aim to get the the person's voice frequency so that we could tell his/her vocal range (i.e. Soprano, Alto, Bass, Tenor). We are very interested in your project here, and we would like to utilize some of your techniques. We were just wondering how we could get the frequencies. Instead of displaying it on the screen, how could we get the frequencies of the voice each second and could we possibly put the values in an array or arraylist? If so, could you help us locate the specific part of your code that could help us accomplish this?
 
Thank you for your time, and I hope for your reply Big Grin | :-D
AnswerRe: Question on how to get the frequencies Pinmemberhazeljane13-Mar-09 3:49 
GeneralRe: Question on how to get the frequencies PinmemberJeff Morton13-Mar-09 10:34 
GeneralRe: Question on how to get the frequencies Pinmemberafmf23-Oct-09 1:54 
GeneralRe: Question on how to get the frequencies Pinmemberafmf2-Nov-09 23:38 
GeneralRe: Question on how to get the frequencies Pinmember Muammar©1-Jan-10 0:56 
Questionspectrogram of a wav file Pinmemberplouvou12-Jan-09 9:59 
AnswerRe: spectrogram of a wav file PinmemberTae-Sung18-Jan-09 9:07 
GeneralRe: spectrogram of a wav file Pinmembertortexy2-Feb-09 12:50 
GeneralRe: spectrogram of a wav file PinmemberGeoNav31-Oct-09 1:52 
GeneralDraw waveform for already existing wave file Pinmemberjugal_piet@indiatimes.com5-Jan-09 20:26 
GeneralVery great app PinmemberMr. Yi26-Nov-08 4:31 
GeneralBug in event detection - left channel only is used PinmemberAtis Straujums9-Oct-08 10:43 
GeneralRe: Bug in event detection - left channel only is used PinmemberJeff Morton9-Oct-08 12:16 
GeneralAnother hi! Pinmemberstano24-Sep-08 18:16 
Generalthe file is not saving ...!! PinmemberAshok Nalam9-Jul-08 1:05 
QuestionDisplay Of Frequencies PinmemberRonD25-May-08 4:17 
AnswerRe: Display Of Frequencies PinmemberMember 47088011-Aug-08 15:24 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Mobile
Web01 | 2.8.140415.2 | Last Updated 28 Jan 2008
Article Copyright 2008 by Jeff Morton
Everything else Copyright © CodeProject, 1999-2014
Terms of Use
Layout: fixed | fluid