Academic Company Events NI Developer Zone Support Solutions Products & Services Contact NI MyNI
This Document is not yet Rated  Rate this Document

Artifact Click Generated On the Analog Output Channel When Driving Speakers

Primary Software: LabVIEW Development Systems>>Full Development System
Primary Software Version: 5.1
Primary Software Fixed Version: N/A
Secondary Software: Driver Software>>NI-DAQ
Hardware: Multifunction DAQ (MIO)>>E Series>>DAQPad-6052E for USB w/Mass Term, Multifunction DAQ (MIO)>>E Series>>DAQPad-6052E for Ethernet w/BNC Term, Multifunction DAQ (MIO)>>E Series>>PCI-6052E, Multifunction DAQ (MIO)>>E Series>>DAQPad-6052E for IEEE 1394 w/BNC Term, Multifunction DAQ (MIO)>>E Series>>PXI-6052E, Multifunction DAQ (MIO)>>E Series>>DAQPad-6052E for Ethernet w/Mass Term, Multifunction DAQ (MIO)>>E Series>>DAQPad-6052E for IEEE 1394 w/Mass Term, Multifunction DAQ (MIO)>>E Series>>DAQPad-6052E for USB w/BNC Term

Problem: I receive some spurious output during my simultaneous analog input/output operation. I based my VI on the SimulAI_AOSWtrigger example VI. I am generating a short burst of noise that is played through a small speaker connected to the analog output channel 1. When the acquisition/output starts, there is a very soft but audible click from the speaker (there is a 200 msec delay before the sound is generated). Can I eliminate this and what is the reason for this spurious signal?

I am using Labview 5.1 with a PCI-6052 card on Windows 98.

Solution: You might be outputting the same data that you are trying to input. Complete the following steps to check for this behavior.
  1. Check the amount of data you are sending to AO Write and the size of the buffer you are setting at AO Config. The amount of data should inititally equal at least the size of the buffer. The reason is that the first time you write to the channels, you will have gaps if you do not fill up the buffer.

  2. Check for a discontinuity between what is on the Analog Output (AO) channel just before and just after beginning the output. A sharp discontinuity causes the speakers to click. An AO channel stays at the last value sent to it so when you generate a waveform, there is always a potential discontinuity between the current and previous values of the analog output, which might result in a click. Some sort of short ramp, short relative to the length of the desired output, should eliminate the click. Another possible solution is to set the first and last values of the waveforms to 0.

  3. If you are sending a binary file of data to the output channels for the sound, check that there is no header information at the beginning of the file. This would seem like a delay of silence, but might actually be sound.

  4. Double-check that you created the sound file as expected. WAV files are usually used, and one of the links below describes how to create a WAV file from an acquisition.


Related Links: KnowledgeBase 297DGK5T: Why Does My Buffered Analog Output Transfer Pause at Times?
KnowledgeBase 0CMAA28Q:  NI-DAQ Regenerates the First Buffer with Circular Buffered Analog Output.
KnowledgeBase 11NHM905: How Do I Play .WAV Sound Files from LabVIEW?


Attachments:





Report Date: 08/22/2001
Last Updated: 06/23/2004
Document ID: 2CLDTAYF

Your Feedback! poor Poor  |  Excellent excellent   Yes No
 Document Quality? 
 Answered Your Question? 
  1 2 3 4 5
Please Contact NI for all product and support inquiries.submit