EGR 103/DAQ Audio 1

This page contains pictures and graphs related to DAQ 3 for EGR 103. It has been updated for Fall, 2014.

IMPORTANT NOTES

• The wiring audio wiring should already be in place. You can check the wiring using the Audio Setup section below, but you should not need to make changes.
• The speakers below the monitors need to be on, and there should be a blue light in the center of the speaker. The volume of each should be on full. Also, the computer attached to the monitor under which the speaker is mounted needs to be awake. Some stations have one speaker like this; others have two.
• At some stations, sound will only come out of one side so be sure to listed to both headphones to see which it is.
• Be sure to start the 32-bit version of MATLAB!

Typographical Errors

• In the table of sampling rates, change the 500 to 1000. For some reason, the latest and greatest version of MATLAB will not play sounds atsampling rates below 1000.
• There are changes to checking the volumes and the audio path...

Audio Setup

You may need to carefully connect various wires to get the audio path to work correctly - though for lab sections after section 1 this should already be done! You can check to see if things are already connected with the following crudely drawn PDF Crudely Drawn PDF.

If you do need to connect wires, please do not start until Dr. G says to, but the following is a guide for which wires go where. First, make sure you have a 6' cable that has audio jacks at both ends and a 6' cable that has an audio jack on one end and alligator clips on the other.

Next, determine if both computers at your lab station have speakers under the monitor or not. The ones where the non-DAQ computer is without a set of speakers should have an audio splitter already attached to the front of the computer.

Stations Needing An Audio Splitter

• One end of the 6' headphone jack-to-headphone jack cable should be connected to the front microphone jack of the DAQ computer. The other end will be connected to your audio source.
• One end of the 6' headphone jack-to-alligator clips cable should be connected to one port of the audio splitter coming out of the headphone jack at the front of the DAQ computer. The other end will be attached to wires that connect to the breadboard and connection block.
• The green speaker jack from the DAQ computer's speaker bar under the monitor should be connected to the other port of the audio splitter.
• You and your partner should connect your headphones to the two ports on the left side of the speaker bar under the DAQ computer's monitor.
• Turn on the speaker bar under the DAQ computer's monitor and set the volume to about half to start. You will adjust this later.
• Summary:

Cable	Connection 1	Connection 2
jack/jack	front microphone jack of DAQ computer	your audio device
jack/clips	output port of audio splitter at front of DAQ computer	red/black wires
DAQ speaker green	output port of audio splitter at front of DAQ computer	N/A
Audio Splitter	headphone at front of DAQ computer	N/A

Stations With Two Monitor-Mounted Speakers

• One end of the 6' headphone jack-to-headphone jack cable should be connected to the front microphone jack of the DAQ computer. The other end will be connected to your audio source.
• The green speaker jack from the non-DAQ computer should be plugged into the headphone jack at the front of the DAQ computer. Effectively, this will turn that non-DAQ computer's speaker bar into the audio splitter. Be sure the speaker bar at the non-DAQ computer is on and the volume is set to full.
• One end of the 6' headphone jack-to-alligator clips cable should be connected to one port on the left side of the speaker bar under the non-DAQ computer. The other end will be attached to wires that connect to the breadboard and connection block.
• The green speaker jack from the DAQ computer's speaker bar under the monitor should be connected to the other port on the left side of the speaker bar under the non-DAQ computer.
• You and your partner should connect your headphones to the two ports on the left side of the speaker bar under the DAQ computer's monitor.
• Turn on the speaker bar under the DAQ computer's monitor and set the volume to about half to start. You will adjust this later.
• Summary:

Cable	Connection 1	Connection 2
jack/jack	front microphone jack of DAQ computer	your audio device
jack/clips	output port of non-DAQ speaker bar	red/black wires
DAQ speaker green	output port of non-DAQ speaker bar	N/A
non-DAQ speaker green	headphone at front of DAQ computer	N/A

Volume Control

To get the volumes set correctly, you will do the following:

• Turn any speaker bars you have to full volume.
• Make sure both computers are "awake" - if a computer goes to sleep, it takes the speaker bar with it!
• On the DAQ computer:
  • Right-click the volume icon at the lower right of the screen and select "Volume Mixer"
    • Set the "Speakers" volume to about 75% of maximum
    • Close the Volume Mixer
  • Right-click the volume icon at the lower right of the screen and select "Recording Devices"
    • Go to the recording tab
    • The "Microphone" should be the default device. If you play music from your music device, the green bars by Microphone should light up.
    • Select the "Microphone," then click "Properties"
      • In the Listen tab of "Properties," select "Listen to this device"
      • In the Custom tab - if there is one - turn off the Microphone Boost
      • In the Levels tab, set the level to about 50%. If there is a Microphone Boost here, turn it off.

Now play sound from your device. You should hear it through the headphones, though possibly only from one headphone.

Others

Let Dr. G or a TA know if you are at a different kind of machine from those described above.

Oscilloscope

Note that five of the DAQ-enabled machines in B209 have newer DAQ cards. Those cards have different voltage ranges from the rest of the cards - anywhere the lab mentions setting limits to [-0.5 0.5], the newer cards will actually have to use ranges of [-1.0 1.0]. These machines with newer cards are identified by the dark gray cable connecting the DAQ card to the CB-68LP versus a light gray cable. Also, the dark gray cables have RoHS compliance stickers. The particular machines are listed on the lab computers page.

Sample Screens

Proper Setup

Here is an example of a sound file being played at the right volume:

Too Loud

Here is an example of a sound file being played at too high a volume:

Note that the top of the signal hits 10 divisions above the Ch1 pointer. Basically, the signal may be going above 0.5 V, but the DAQ card is not set up to handle voltages that high, so it "clips" the value to 0.5. This will lead to poor sound quality.

Won't Stop!

If the "stop" button does not seem to work, just close the whole oscilloscope.

Troubleshooting

Values not centered

First, note that the Ch1-> on the left side of the screen points to 0V; because you have two channels on, Channel 1 will show up "centered" in the lower part of the oscilloscope window (see the above picture in the Proper Setup section). If the issue is that one side of the signal is clipping, or the signal has an average that is not at the Ch1-> spot, the most likely problem is that the black and green wires connected to Lines 66 and 32 are either connected to the wrong place on the DAQ card or on the breadboard.

No sound

Several possible causes. Make sure all the wires are plugged in correctly and completely. Make sure the speakers are on and awake. Make sure the red and black clips are connected to metal (not insulation) and also that they are not touching.

Weird Errors

The following have been happening semi-randomly:

• softscope issues:
  • Opening softscope gives an error about the GUI - restart the computer you are on.
  • The "stop" button will not work - close the softscope window. This may lead to the following problem:
  • Closing softscope closes MATLAB - just restart MATLAB. This may happen a couple times... If it keeps happening, just use softscope to get your volumes correct, restart MATLAB, then skip to the next part of the lab without reopening softscope.

Frequently Asked Questions

How many songs do we need?

You will only need one song; in your group, pick which of the music sources you want to use.

How do we connect our music source?

• If you are using a standalone device - your own MP3 player, for example - connect the black cable that is coming from the back of the DAQ computer to the headphone jack of your device.
• If you are playing a song off a CD or memory stick, use the other computer and plug the black cable from the back of the DAQ computer to the headphone jack at the front of the other computer.

What if I only hear sound out of one side of the headphones?

That's normal - some of the audio splitters we are using are monaural, so you will only hear sound on one side.

What do you mean by "What was the maximum voltage the DAQ measured...?"

When you figured out the level for the various volume controls, you were looking to make sure the signal peaked at a particular value. What was that prescribed value and why did you want to make sure your signal did not generally exceed that?

What do you mean in Question 5?

Compare the quality and the number of songs for each sampling rate - is it possible that something of CD or iPod quality would store that many songs? For example, if something is very high quality and would store only one song on a CD, that is probably not how files are stored on a CD...

Questions

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