IBM PCjr Hardware Maintenance And Service page 156

When you start the next part of the test, you will hear a
low-frequency sound coming from the external speaker
(not the system unit). The sound's frequency (pitch)
increases smoothly until it reaches 523 Hz and holds
steady. Then its volume diminishes untU the sound is
gone.
Another sound symbol will appear on the screen.
As you do this part of the sound test, Usten for these
failures:
1. No sound is heard at aU.
2. Something other than a smooth increase in
frequency occurs.
3. The volume diminishes abruptly rather than
smoothly.
Note: You may hear the volume decrease in
small steps. This is normal and is not a failure.
CONTINUE
Sound 3-820-3