ANR Headsets real and apparent attenuation question?

[Pelikanpete]

I've copied this over from the Medical and Health section (no responses) and would be interested in people's opinions. It seems to be taken for granted that some headsets protect your hearing when maybe they don't.

I've been researching buying a new headset recently and was deciding whether to go for ANR or not. There are hundreds of posts about the topic and it is clear that the general consensus is that if you have the money to spend, ANR is well worth having.

The most popular ANR headset seems to be the Bose Aviation X, with the main criticism being that it has poor passive attenuation (ie. provides little hearing protection with the ANR switched off).

Most dismiss this as not being a problem as it's a simple case of making sure the batteries don't run out. They also point out that although the Bose X is very expensive it's worth getting the best when the alternative is permanent noise induced hearing loss.

So I did a bit of Google work to find out more about ANR and I have found out that ANR technology only really works for lower frequencies and provides no protection for the higher frequencies (that are less audible to the human ear but are still damaging). It seems good ANR also needs good passive attenuation to block the higher frequencies.

Does this mean that headsets with good active (ANR) attenuation but poor passive attenuation, like the Bose X, should not be used in a lot of general aviation aircraft as they will result in the user suffering hearing loss?

If so Bose and others manufacturers should clearly warn users of the danger and make it clear which aircraft categories they are effective in. General aviation pilots might then know to choose ANR headsets that also offer high passive attenuation.

[IO540]

There is more to this.

A lot of the noise in a GA plane is from the exhaust, but very much is from the rotating prop slipstream which hits the cockpit all around and vibrates the cockpit material.

I have recently done some measurements on this.

The engine fundamental frequency (crankshaft rotation) barely features - except at idle. The piston frequency (6th harmonic of a 6-cyl) does feature but not strongly.

Most of the noise peaks at mid-range (~ 250Hz) but is otherwise quite broadband and ANR headsets can and do work well on this. There isn't much (on piston planes) into the kHz range, on which ANR doesn't work and only heavy passive attenuation would be much good.

The Bose X headset is suprisingly, after all the years, still the best. There are suggestions that the Lightspeed Zulu (never tried it myself) is close though. The rest of the 'pilot shop' headsets are pretty poor compared to the Bose X.

Another issue is that ANR headset attenuation is heavily misrepresented in the adverts. Bose carefully avoid making any db claims in their adverts. Others, notably Pilot Industries, make various claims like "22db additional noise protection" which suggests their ANR gives you another 22db, which is rubbish - it's 5-10db or so. I had one of these and eventually sent it back to Pilot on grounds of the ANR barely working and the mfg confirmed it was to spec. The Bose ANR is very much more effective though. Sadly you get what you pay for in headsets and the cheap ones that cover the pilot shop shelves are just that ... cheap.

The Bose X is perfectly usable with no power which is good enough IMHO.

There are David Clarke headsets which are as good as the Bose for attenuation but they do it with heavy clamp pressure, which does your head in after 1-2 hrs. The Bose does the same with far less pressure and is OK to wear for 6+ hrs.

The downside of the Bose is that it is not so good for being kicked around and sat on etc. For that kind of usage you want to buy a dirt cheap headset. For yourself, get the best.

[Pelikanpete]

Whilst comfort and clarity are clearly very important, headsets are also meant to be protective equipment. It seems strange that they are not regulated by any industry standard testing and that they do not have to display their rating at providing hearing protection. Especially when you consider that companies issuing them have to conform to so much health and safety at work legislation.
A simple graph showing attenuation against frequency and an indication of aircraft category suitability would clear up any confusion when comparing different models and makes of headsets.

[18greens]

Pelikan, you make a good point but the figures do not add up against the experience.

On a headset with poor passive attenuation the active section when turned on will sound more impressive - but is that what you want.

Any active headset is better than passive for long periods in the cockpit and they make radio reception much clearer. You should also consider the number of hours spent in the cockpit. If you are an instructor pushing 4-5 hours per day the outlay is worth it. If you spend 1-2 hours per month are you going to notice.

For me I would buy either the Dc 10-13.4 passives or the Bose and I would not bother with anything in between. Bose are the daddies, make sure the batteries are kept charged and enjoy top quality aviation sounds.

[Mike Cross]

I'm no expert but my understanding from when I was in the Army is that high frequencies are much more damaging than low. This became a problem when the forces adopted higher velocity weapons which produced a much higher frequency pulse of sound when the bullet leaves the muzzle.

I believe what happens is the bones of the inner ear get damaged by the vibration where they meet. I'm not aware of any significant problem with hearing damage from leisure aviation in normal SEP. ANR is more to do with reducing fatigue and increasing intelligibility IMHO.

[BigEndBob]

When i have flown checkouts with pilots with ANR mixed with my Dave Clarks its really annoying as they seem to use cheap microphones feeding loads of aircraft noise into the intercom and my headset.
After 30 years flying and twenty with DC's averaging 600 hrs a year in GA theres been little hearing loss other than that associated with age.

Try hanging around a forge for 5 years with high frequency generators and electric motors, then try to sleep at night, thats what i call hearing damage.

Whats more tiring is the constant babble on the radio.

['Chuffer' Dandridge]

Whats more tiring is the constant babble on the radio.
I'll second that!!

Dave Clarkes are the ones to buy. Good attenuation, but with ANR, even better. Slightly bulky though but worth it to save your hearing.

Used a mate's BOSE-X headset the other week in a quiet aeroplane (turbine)and thought it was crap! Heaven knows what it would be like in your average flying club Cessna.

[kalleh]

Used a mate's BOSE-X headset the other week in a quiet aeroplane (turbine)and thought it was crap! Heaven knows what it would be like in your average flying club Cessna.

Sounds like you forgot to turn it on....

I don't think pilots flying low hours will benefit less from ANR, they will benefit more. I switched to ANR in the middle of my PPL training, and started flying better! Reason? This was a busy Florida airport and with the passive headset I was struggling to keep up with ATC, but with my Lightspeed 25xlc the transmissions were crisp and clear. That meant I could focus more on my flying instead of RT.

As a bonus I also felt less fatigued after my longer lessons, but that might just be psychological effects :)

Of course, I have never tried a pair of high-end passive headsets either, so maybe it is just an unfair comparison.

[whitehorse]

"Used a mate's BOSE-X headset the other week in a quiet aeroplane (turbine)and thought it was crap!"

My company has within the past 2 years issued all crew with Bosse-X, we fly 4 and 2 engine, older type, turbo props. The noise reduction/comfort is really noticeable, after a long day, no more ringing ears at night:).

Don´t forget to adjust the settings on the headset volume control for the best effect. I´m not going back to DCs.

WH

[IO540]

Used a mate's BOSE-X headset the other week in a quiet aeroplane (turbine)and thought it was crap!

Must have been faulty or not switched on.

The Bose X is an excellent headset. I have four of them in the plane. Everybody who is a pilot and has flown with me is amazed how much better they are than theirs.

OTOH, the £300 Bose ANR headsets which are sold at Dixons etc for airline passenger wear seem to be a lot worse - based on my test of one of these. It got sent back.

[172driver]

What perhaps amazes me most with the Boses is the VERY noticeable drop in fatigue after long flights. You simply don't feel worn out after 5 or 6 hours in the cockpit. And no ringing ears either :ok:

[Cobalt]

OTOH, the £300 Bose ANR headsets which are sold at Dixons etc for airline passenger wear seem to be a lot worse - based on my test of one of these. It got sent back.

No surprise there. The airline passenger headset has to be optimised for an airliner cabin, in which noise is of higher pitch than in a piston-engined aeroplane, and has no need for low-frequency attenuation. Horses for courses.

The Bose-X appears to be an allrounder, though - it works as well as (actually a bit better) than the passenger headset in an airliner cabin.

What perhaps amazes me most with the Boses is the VERY noticeable drop in fatigue after long flights. You simply don't feel worn out after 5 or 6 hours in the cockpit. And no ringing ears either

ANR works very well for lower frequencies and less so for higher frequencies. By low I mean 50-500 Hz. Above that an ANR headset is just any other passive headset. This is ideal for prop aircraft (2-blade prop pulse: 80 Hz, 3-blade prop pulse - 120 Hz, all at 2400 RPM, 4 cylinder firing/exhaust pulse: 80 Hz).

Passive attenuation works better at higher frequencies.

Bose's give up some passive attenuation to give you more comfort - they have noticably lower clamping pressure than most other headsets.

An "old design" good passive headset with an ANR cicruit added can be quieter than the Bose, but it still squeezes your head like a vise.

If you consider buying a headset in that price range, I would recommend to get them and wear them for several hours at a time. Otherwise you will not appreciate the difference. The Boses are not neccessarily the quietest anymore, but they are very quiet and very comfortable.

When you borrow some from a friend, check if it has the sheepskin cushion on the headband, not the old foam ones. These could give you a headache after an hour or so because they can create point pressure unless you wear the headset at a perfect angle - the only real flaw the 1st generation Bose-X had.

[IO540]

No surprise there. The airline passenger headset has to be optimised for an airliner cabin, in which noise is of higher pitch than in a piston-engined aeroplane, and has no need for low-frequency attenuation.

I didn't test the £300 Bose in any plane. It was tested informally against various noise sources at home. Didn't seem to do anything much, and it also whistled.

['Chuffer' Dandridge]

Sounds like you forgot to turn it on....


D'oh, I know I'm a pilot but I ain't dat tick!:ugh:

What I meant was it was like wearing one of those old Airlite 62 headsets, but with ANR. Maybe I just prefer some passive attenutaion as well...

DCs for me.:ok: