A320 CVR Test Loudspeaker Off

[slate100]

Why does the Loudspeaker need to be fully off when doing the CVR test?

[pineteam]

Yeah, I don't understand either. Before, on the older models, it was only required to set the parking brake ON and press the test button and that was it. Then they changed the procedure and it requires loudspeakers off and intercom ON with audio knob at minimum... But the test still works even without doing it. Weird. xD
I'm interested also to know why.

[compressor stall]

Does another Airbus type need it to be? Occasionally things get changed on the 320 with the introduction of new types (eg A350) for commonality and CCQ minimisation.

[AviatoR21]

It’s due to the Larsen effect! Pretty sure it’s in the notes in the FCOM.

[FlightDetent]

The CVR test is successful when an audio test signal is heard through the loudspeakers and the CVR TEST pb is pressed and maintained. Depending on the CVR model, the audio test signal is:

For CVR 30 minutes:
‐ A continuous tone, or
‐ A short tone.

For CVR 120 minutes:
‐ A short tone, or
‐ A short tone and a beep every 4 s, or
‐ Two short tones and a beep every 4 s.

The audio test signal stops when the CVR TEST pb is released.

Note: ‐ The flight crew may also hear an acoustic feedback (i.e. Larsen effect) during the test. The test is still valid even if this acoustic feedback (i.e. Larsen effect) is heard.
‐ If the flight crew cannot hear the audio test signal through the loudspeakers, and if the CVR maintenance headset (22RK headset) is available, the flight crew can perform the CVR TEST through the CVR maintenance headset.
‐ If an acoustic feedback (i.e. Larsen effect) is still heard, the flight crew can perform the CVR TEST using the 22RK headset and with the parking brake set to off. Before setting the parking brake to off, the flight crew must ensure that chocks are in place or brakes are applied. Set the parking brake to on when the CVR TEST is achieved.
‐ If no 22RK headset is available, the Larsen effect can also be reduced by preventing the cockpit ambient microphone from picking up the ambient sound (i.e. by temporarily covering it during the test).
Those are just the explanatory remarks printed below the to-do actions required to perform the test, of which there are exactly TWELVE! Where is the puking emoticon when you need one?

FD - an Airbus aficionado of 25 years: when I will change type and get cold feet about the move, I'll have this printed in the flight bag. Seriously.

[Escape Path]

Yeah, I don't understand either. Before, on the older models, it was only required to set the parking brake ON and press the test button and that was it. Then they changed the procedure and it requires loudspeakers off and intercom ON with audio knob at minimum... But the test still works even without doing it. Weird. xD
I'm interested also to know why.

Bumping this old thread precisely because of what Pineteam says. I'm curious as to why do we need to do the other actions (Intercom sw to INT, but volume at minimum...) to test the CVR even if the test is satisfactory just with the parking brakes on. I'm sure there's a reason for it but it's absolutely baffling why we need to do that if the test is OK anyway...

[noptawat]

Why does the Loudspeaker need to be fully off when doing the CVR test?

Also on APC RAD/INT Selector to INT position.

INT knob pop-up and fully counter-clockwise.