Noise Footprint to height ?

[Vfrpilotpb]

Picture this, very bright moonlight, nil wind, in fact a night as peaceful as John Prescotts concience, sounds of rotors approaching fast, powered by a turbine, the As350 of my local constabulary passes right over my house, and Bingo exactly 6 counted seconds the noise has gone, total footprint about 12 to 13 seconds, to those of you who know these things, would this point to a very fast and low alt journey, or a new sort of "Whisper mode" to sneak up on Billy Burglar, I must admit to being a little puzzelled?

[Thomas coupling]

Hi VFR, how's life?

Wouldn't be a 350, has to be a twin (355).

Min height at night over built up area: 500'.

Squirrels are noisy anyway.

Are you saying that it sounded low or noisy?

[ATPMBA]

Could it have been an EC-120 ? I believe one of those flew over my house last summer and once it passed over the noise quickly faded away.

[Vfrpilotpb]

Hi T-C

I am pretty sure the ASU at Warton are still on the AS355 ( my slip saying AS350) I am trying to find out if there is any way that height can be correlated to the footprint, there is a guy at Clitheroe has a new 109, the CPL fly's it at about a fixed 2000ft and you can hear that machine for minutes before he passes over, but the one that got me thinking was the AS355 to which my first post referred, then again I suppose 500ft and a pretty fast flight may keep the footprint down quiet a lot, not looking to complain, just stretching my thoughts a little.

T-C I hope that you are well, and still chasing motor bikes
we had an AS350 with us two weeks ago, what an incredible machine, didn't know such things could be done with these birds!

[The Nr Fairy]

I hope I never get a commercial job to Clitheroe - I don't think I'd be able to find it.

Sorry, Vfr - couldn't resist !

[Thomas coupling]

VFR: the guys at Warton have receipt of their all singing all dancing £2.8 million, EC135 IFR EFIS CPDS.....you won't hear it...it's got whisper mode, on

Only jealous.............take care.