Cabin Alt. Fluctuation
 

Please excuse me if I'm intruding,

Years ago I was on a domestic flight aboard either a 737 or A320 at cruise alt. when my ears popped 4 to 5 times in a row. The popping were at consistent intervals and lasted for ~1 or 2 seconds. I do not recall if there was mechanical background noise during the event due to the hearing degradation the popping caused. When the fluctuation ceased it seemed to return to the preset pressure because my hearing was clear as it was before this whole event.

The flight attendants were on the aisle with service carts, and did not react to this anomaly. I believe I heard another passenger mumble "what was that", but it was left unanswered.

Can someone shed some light on this?

Thank you

My guess would be the outflow valve(s) reacting to an over pressure situation.

Outflow opens when overpressure sensed, pressure diff drops, so outflow valve starts to close, pressure diff increases, so over pressure relief opens the outflow valve again.

Hi there,
I agree with Capt. Claret. In the 737ng sometimes when the vacuum toilets are flushed, the cabin pressure will momentarily drop and the correction made by the pressurization system can sometimes be a little harsh.

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As Mr B says, the most likely 'culprit' is/are the loos. Every flush can be seen on the cockpit cabin altitude indicator (in a 7373NG) so it obviously causes a momentary 'loss' of cabin pressure. I would think it unusual for someone's ears to be affected, though.

Someone had dire-ear? :E

Thank you for all the replies.

I would like to add that I only experienced this phenomenon once during the entire flight.

In poor description, the effect was something like "popopopo" for a duration of 1~2 secs. In other words, a "pop" occured every ~1/4 of a second.

Just goes to show the superiority of the Douglas inspired Boeing (717). Three vacuum dunnies and never noticed any pressurisation glitches when they're flushed! :p