Announcement

Collapse
No announcement yet.

Hissing sound during and after playing wave file

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Hissing sound during and after playing wave file

    Hi,
    I have a very strange and annoying sound effect on my uLCD-24PT:
    When playing a wave file, you can hear the recorded sound, but it is overlaid with a high frequency, hissing tone. This hissing sound continues even after the wave file has finished playing.

    The input files are Windows-Wave Files generated by a Text 2 Speech program.
    RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 8000 Hz

    I tried out different loudspeakers (8Ohm), but no luck.

    Version 0.000 [56 00]
    Get Status 0.016 [7A]
    Version 0.109 [56 01]
    Micro-LCD
    Hardware Revision: 10
    Firmware Revision: 19
    H res: 240
    V res: 320

    An acceptable quality of the sound output is really important for my project ...

    Best regards & many thanks for your help in advance !
    Wolfgang

  • #2


    From the manual


    The ideal sample rate of the WAV file is 16Khz-Mono and the maximum should be 22Khz.

    Any higher sample rate will extremely slow down the system. Sample rates below 12Khz, the PWM will cause aliasing (filtering is a bare minimum).


    So what you are hearing is the aliasing (and/or the 8khz 'carrier').



    Change your sample rate to 16 to 22khz and it should sound better
    Mark

    Comment


    • #3


      Thanks a lot - that solved the problem !!!

      Best regards,
      Wolfgang

      Comment


      • #4


        If I need to be sure any audio file I play is in this range, how can I tell what the sample rate of a file is? All windows will tell me is the bit rate. Example, laser.wav is 176kbps according to the properties dialog in windows.

        Dan Clemens
        Summerville, Oregon

        Comment


        • #5


          Upgrade to XP XP tells you the sample rate

          I'm sure there should be (free) utilities out there that give you that information.

          http://www.4dsystems.com.au/code/index.php?node=77&id=85 is a 4DGL utility that tells you
          Mark

          Comment


          • #6


            running windows 7 (grin) but will try it in XP mode and thank you for the utility!

            Dan

            Comment


            • #7

              found a bug in the WaveDemo.4dg program, line 151 should be un-remarked and line 152 should be remarked. Otherwise all of your wave files on the chip look just like DING.wav
              Also in the following program:
              Code:
              #platform "uLCD-32PT_GFX2"func main()snd_Volume(127);print("\nstart.\n") ;pause(5000);file_Mount();print("\nNow Playing\n") ;file_PlayWAV("POLICE.WAV");pause(5000);snd_Stop();print("\nstop.\n") ;file_Unmount();pause(5000);endfunc
              the hissing noise begins right after POLICE.WAV finishes playing and does not stop untill 'endfunc'. Any other way to turn it off?

              Dan Clemens

              Comment


              • #8


                wkorosec wrote: Hi,
                I have a very strange and annoying sound effect on my uLCD-24PT:
                When playing a wave file, you can hear the recorded sound, but it is overlaid with a high frequency, hissing tone. This hissing sound continues even after the wave file has finished playing.

                The input files are Windows-Wave Files generated by a Text 2 Speech program.
                RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 8000 Hz

                I tried out different loudspeakers (8Ohm), but no luck.

                Version 0.000 [56 00]
                Get Status 0.016 [7A]
                Version 0.109 [56 01]
                Micro-LCD
                Hardware Revision: 10
                Firmware Revision: 19
                H res: 240
                V res: 320

                An acceptable quality of the sound output is really important for my project ...

                Best regards & many thanks for your help in advance !
                Wolfgang
                Hi, I have very similar "hissing" problem with my uLCD-32PT_GFX2. The actual sond is fine but I get also the hissing in the background. It starts (the hissing) just before the actual wav and then just keeps hissing until system reset. The thing is though that I'm using sound files which meet the requirements (supplied by 4D Systems). Another interesting thing is that when the touch function is disabled the hissing stops but it restarts once the touch function is reactivated.
                Only reset stops the hissing...

                The idea is to play a little sound every TOUCH_PRESSED...

                Any help would be greatly appreciated...

                Thanks

                Marek

                Comment


                • #9


                  Read the rest of this thread, the answer (and explanation) are there
                  Mark

                  Comment


                  • #10


                    Sorry to be a pain, but could you please be more specific?

                    I've just tested it a bit and it looks like the hissing is present only when the touch function is enabled. I don't think this has been mentioned in the thread?

                    Thanks

                    Marek

                    Comment


                    • #11


                      Sorry, missed the bit about touch. Will need to investigate.
                      Mark

                      Comment


                      • #12


                        Any news?

                        Comment


                        • #13


                          The audio amplifier is left turned on after any sample is played, this is done
                          to substantially eliminate clicks between samples. Unfortunately, the action
                          of scanning the touch pad generates a lot of audio hash which is picked up by
                          the amp. Manually disabling the audio amp when you have finished playing should solve this.

                          pin_HI(AUDIO_ENABL); // turn off audio amp.

                          Amp will be automaticaly turned back on next time you play a file.
                          Regards,
                          Dave

                          Comment


                          • #14


                            Hi, I have the same hissing problem using the uLCD24-PT, but using the direct audio output, not the on-board amplifier. The problem is that the direct output CANNOT be disabled using the pin_HI(AUDIO_ENABL); command. The audio output is just UNUSABLE as is for my application!!!
                            Do you have another solution, maybe by replacing or adding some componets?
                            I personnaly think that this is a terrible hardware design issue and I can't understand why it has not been fixed in the latest hardware versions. I have tried with a uLCD-32032-P1T I bought more than two years ago and the problem is the same!!! So please FIX this problem for next hardware version, thank you very much.

                            Comment


                            • #15


                              If you want to you can try this.



                              Connect side of R21 that heads off towards the Picaso Chip, to, say, the joined inputs of a gate from a 74LC08 (with clean 'analogue' power, or at least well decoupled with eg 470r/4u7).



                              Connect the output of that gate to a string of three 2k2 resistors and connect each of the resistor joins to gnd via 0.01uf.



                              Connect the last 2k2 to your amplifier
                              Mark

                              Comment

                              Working...
                              X