AMBIENT NOISE SENSOR

[Danial9874]

Helo

B737 uses low pressure switch to increase pax cabin speaker approx 6dBs when engine is running
Is there any aircraft that use Ambient noise sensor to automatically increase sound level of cabin speaker ?

thank you

[lochias]

Normally there is a logic behind automatic gain in PA system and it involves engine running input, all doors closed etc.

see 737 schematic interface below engine running relays
https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/831x518/737_a109b32889d5dfbfccb5be883d26e0d146527c60.jpg

[greatwhitehunter]

The B777 uses ambient noise sensors in the cabin. They monitor the local sound level and filter the noise and signal to compute the signal to noise ratio. The result is used by the system to control the PA level in that zone. If memory serves there are 5 PA zones. This is in addition to the normal discrete inputs mentioned above which increase PA level for engines on, A/C speed, decompression etc. The cabin crew can turn the ANS system off if it becomes troublesome, (and it does).