Re: Stepping back from ANR

[Larry Dighera]

On Sat, 26 Aug 2006 23:41:41 GMT, B A R R Y
> wrote in
>:

>The true value of the money I spent
>on the expensive set was unbelievably apparent.

There is no question that Active Noise Reduction headsets offer
superior intelligibility and less stress than passive headsets.
However, I doubt the difference in cost among ANR headsets is
indicative of their performance.

[John Gaquin]

"Larry Dighera" > wrote in message
>
> There is no question that Active Noise Reduction headsets offer
> superior intelligibility and less stress than passive headsets.

Query: I haven't flown a light plane since 1981, so I've never had the
occasion to use ANR. When in use in a typical light single like a 172,
etc., can you hear the engine, or the airflow, or even your passenger
speaking (without benefit of an intercom)?

[Dan Luke]

"John Gaquin" wrote:

>> There is no question that Active Noise Reduction headsets offer
>> superior intelligibility and less stress than passive headsets.
>
> Query: I haven't flown a light plane since 1981, so I've never had the
> occasion to use ANR. When in use in a typical light single like a 172,
> etc., can you hear the engine, or the airflow, or even your passenger
> speaking (without benefit of an intercom)?

ANR mutes a lot of the low freq. noise. It's kind of like listening to the
world through speakers with the bass turned all the way down.

It doesn't suppress the sound of a human voice in the cabin much; it may
even make it more intelligible. You can still hear the engine, but if you
couldn't hear the airflow with a passive set, you won't hear it with an
active one either.

--
Dan
C172RG at BFM

[Jose[_1_]]

> ANR. When in use in a typical light single like a 172,
> etc., can you hear the engine, or the airflow, or even your passenger
> speaking (without benefit of an intercom)?

Yes.

ANR reduces the background noise. Anything different from the
background noise is not reduced (anywhere near as much). And even if it
were, your ear becomes more sensitive because it's no longer assaulted
by the din of the background noise.

Jose
--
The monkey turns the crank and thinks he's making the music.
for Email, make the obvious change in the address.

[John T[_2_]]

"John Gaquin" > wrote in message

>
> Query: I haven't flown a light plane since 1981, so I've never had
> the occasion to use ANR. When in use in a typical light single like
> a 172, etc., can you hear the engine, or the airflow, or even your
> passenger speaking (without benefit of an intercom)?

I can hear the crinkle of un/folding my charts while in flight. I've also
heard fingers snapping. :)

--
John T
http://sage1solutions.com/TknoFlyer
Reduce spam. Use Sender Policy Framework: http://spf.pobox.com
____________________

[Andrey Serbinenko]

DC claims additional 17-22dB noise attenuation with ENC turned on;
regular foam earplugs are said to do around 32dB of attenuation. Seems
even better than ENC, and hell of a lot cheaper, too... Does anybody
have any opinion on that?


Andrey


John T > wrote:
> "John Gaquin" > wrote in message
>
>>
>> Query: I haven't flown a light plane since 1981, so I've never had
>> the occasion to use ANR. When in use in a typical light single like
>> a 172, etc., can you hear the engine, or the airflow, or even your
>> passenger speaking (without benefit of an intercom)?
>
> I can hear the crinkle of un/folding my charts while in flight. I've also
> heard fingers snapping. :)
>

[Morgans[_4_]]

"Andrey Serbinenko" > wrote in message
...
> DC claims additional 17-22dB noise attenuation with ENC turned on;
> regular foam earplugs are said to do around 32dB of attenuation. Seems
> even better than ENC, and hell of a lot cheaper, too... Does anybody
> have any opinion on that?

The active electronic noise canceling works by blocking out "predictable"
repetitive noises, like the beat of the pressure wave coming from the prop,
and the bark of the exhaust. It does not do well on a quick snap, or non
repetitive crackling of charts, or on the changing sounds of speech.

Foam ear plugs work by blocking any, and everything. That means you have to
raise the volume of the communications output, to be able to hear the tower,
or other people talking. That could possible result in over driving the
speakers or the amp driving the speakers, resulting in difficulty
understanding transmissions. That is a bad thing.

Some people that have posted here do regularly wear foam plugs under
headset, and have good results. It seems to be more popular with the open
cockpit group.

I wear foam plugs under a headphone radio while I'm mowing the grass, or
weedeating. It works for me, in those applications. Sure, the music is not
quite as clear, but it doesn't really matter. What does matter is that I
can't stand being blasted by the noise of the mower, or even worse, the
music turned up loud enough to be heard over the din of the mower. <g>
--
Jim in NC

[Roger[_4_]]

On Tue, 29 Aug 2006 19:29:24 -0400, "Morgans" >
wrote:

>
>"Andrey Serbinenko" > wrote in message
...
>> DC claims additional 17-22dB noise attenuation with ENC turned on;
>> regular foam earplugs are said to do around 32dB of attenuation. Seems
>> even better than ENC, and hell of a lot cheaper, too... Does anybody
>> have any opinion on that?
>
>The active electronic noise canceling works by blocking out "predictable"

It shouldn't have to be predictable, or repetitive.
ANRs listen to the ambient noise. They amplify it to a given level and
send it through the head set so it arrives at your ear 180 degrees out
of phase with the noise that leaks through.

>repetitive noises, like the beat of the pressure wave coming from the prop,
>and the bark of the exhaust. It does not do well on a quick snap, or non
>repetitive crackling of charts, or on the changing sounds of speech.

Mine does very well with frequencies from about 3,000 cycles down. If
I want to hear the person next to me, they better be talking into a
mike, or I have to lift one side of the head set to hear them. Nor do
I hear much out of the charts. Some but not much. However due to the
efficient cancellation of the low frequency noise I can hear the
charts. With the ANR function off I can not hear them at all.

Other things I can hear with the ANRs on are the engine accessories.
All sorts of things become audible that are not with the ANRs off.

>
>Foam ear plugs work by blocking any, and everything. That means you have to
>raise the volume of the communications output, to be able to hear the tower,
>or other people talking. That could possible result in over driving the
>speakers or the amp driving the speakers, resulting in difficulty
>understanding transmissions. That is a bad thing.
>
>Some people that have posted here do regularly wear foam plugs under
>headset, and have good results. It seems to be more popular with the open
>cockpit group.

Foam ear plugs are not very effective, but they do have some
attenuation. The newer expandable ones are better but still no where
near as good as a passive head set which is improved by the addition
of active noise canceling.

When I was shooting competitively (Trap shooting) I wore passive ear
muffs (same as the passive head set without the mike), plus I wore
custom molded ear plugs.

The problem with ear plugs alone, be they soft or molded is conduction
of sound by the mastoid bone behind the ear. Even with the most
effective silicone, molded ear plug I could easily hear people
speaking that I could not hear with just the ear muffs which cover
the mastoid bone.

The small head sets do not work at all for me. I flew right seat in a
twin two hours each way. The pilot was an ATP who told me I didn't
need my ANRs as he had a spare set of the ones they used on commercial
flights. With the tiny head set I could not hear the radios well
enough to even handle the communications which was my reason for
going. (GAWD but it was noisy in that Aztec) We were IFR and had
planned on both of us working. Unfortunately I let him convince me
and left my head set in the bag in my car.

>
>I wear foam plugs under a headphone radio while I'm mowing the grass, or
>weedeating. It works for me, in those applications. Sure, the music is not
>quite as clear, but it doesn't really matter. What does matter is that I
>can't stand being blasted by the noise of the mower, or even worse, the
>music turned up loud enough to be heard over the din of the mower. <g>

Get one of those expensive ANRs and plug your radio or player into
that. I've tried wearing ANRs designed for listening only and they
were expensive ones, but I could not hear the radio over the riding
mower noise. Yet the mower is not loud enough to normally bother with
ear muffs or plugs. The weed whacker OTOH...

I've been tempted to wire up my Telex head set so I can listen to the
stereo as well as my HT. I think that would provide enough
attenuation to be useful.


Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Thomas Borchert]

Andrey,

> Does anybody
> have any opinion on that?
>

Yup: Too little data. What method was employed to measure these values?
At what frequencies?

I strongly recommend reading Lightspeed's ANR 1o1 tutorial on their
website. These advertised values mean pretty much zip.

--
Thomas Borchert (EDDH)

[Andrey Serbinenko]

> Yup: Too little data. What method was employed to measure these values?
> At what frequencies?

If I remember correctly, there was a frequency/attenuation chart on the
back of some foam earplugs carton I saw once in a drug store. I'm sure
ANR manufacturers have plenty of charts for their products. So, data is
obtainable, at least theoretically. But that doesn't mean much, since
noise perception is a very psychological thing (think of all those crazy
psycho-acoustic models for Hi-Fi audio noise reduction), and you cannot
really go by "more decibels = better noise cancelling" principle all the time.

Unfortunately, I cannot make comparisons myself, as I don't currently
own an ANR set. I tried passive vs. passive+foam, and the difference was
drastic. But I can't really tell how much I'm losing due to lack of selectivity
of ANR without trying one. Thus the question.

>

Andrey

[Thomas Borchert]

Andrey,

> If I remember correctly, there was a frequency/attenuation chart on the
> back of some foam earplugs carton I saw once in a drug store. I'm sure
> ANR manufacturers have plenty of charts for their products. So, data is
> obtainable, at least theoretically.

A chart alone means nothing. It all depends on how you measure that chart.

> But that doesn't mean much, since
> noise perception is a very psychological thing (think of all those crazy
> psycho-acoustic models for Hi-Fi audio noise reduction),

Not sure about that.

--
Thomas Borchert (EDDH)

[nrp]

Not all ANR headsets work on the same principle.

I understand that most of them are digital, in that they look for
repetitive noise & then use digital algorithims to s-l-o-w-l-y cancel
out the repetitive components of any noise signal. This has the
advantage that they can work to higher frequencies, but limited in that
they only work with repetitive (i. e. cyclic) signals. They are unable
to cancel random noise.

Some (the Headsets Inc version and maybe others) are a broad band
analog bucking system. They do not cancel just a repetitive
excitation, but can also cancel most of any random noise sensed by the
internal microphone system. The disadvantage of this type is that it
can work only at frequencies below typically about 300 Hz. Above this,
and they must rely on the passive noise rejection of the headset cups -
which is pretty good at high frequencies. It is low frequencies that
passive systems have the poorest atenuation.

Anyone else with more of the puzzle?

[Peter Duniho]

"nrp" > wrote in message
oups.com...
> Not all ANR headsets work on the same principle.
>
> I understand that most of them are digital, in that they look for
> repetitive noise & then use digital algorithims to s-l-o-w-l-y cancel
> out the repetitive components of any noise signal.

I've never heard of an ANR headset that doesn't just use digital signal
processing as Roger describes.

Perhaps you could direct us to documentation of one that does the sort of
analysis you're talking about. That would help provide some context for the
discussion.

Pete

[Andrey Serbinenko]

From Wikipedia on "Psychoacoustics":
---
In many applications of acoustics and audio signal processing it
is necessary to know what humans actually hear. Sound, which consists
of air pressure waves, can be accurately measured with sophisticated
equipment. However, understanding how these waves are received and
mapped into thoughts in the human brain is not trivial.

Recognizing features important to perception enables scientists and
engineers to concentrate on audible features and ignore less important
features of the involved system. It is important to note that the
question of what humans hear is not only a physiological question
of features of the ear but very much also a psychological issue.
---

There's more in that article if you're interested.


>> noise perception is a very psychological thing (think of all those crazy
>> psycho-acoustic models for Hi-Fi audio noise reduction),
>
> Not sure about that.
>

[nrp]

On inquiry, I was told by technical people (I suspect it is a garage
shop operation) at Headsets Inc that their rejection system is all
analog. Being somewhat familiar with analog and digital noise
cancelling systems, I can verify that from the HI system that I have.
Oddly enough the performance seems somewhat similar.

[nrp]

On inquiry, I was told by technical people (I suspect it is a
near-garage shop operation) at Headsets Inc that their rejection system
is all analog. Being somewhat familiar with analog and digital noise
cancelling systems, I can verify that from the HInc system that I have.
Oddly enough the final performance seems somewhat similar.

It is easy to talk about a 180 degree cancelling pressure waveform
generator (per Roger above), but that is an over-simplification of the
problem that isn't acheiveable from a real control loop stability
standpoint.

Digital systems get around this by a slow optimization in the frequency
domain over a wide (i. e. hi) frequency range at the expense of being
able to cancel random noise, whereas analog does it in the time at the
expense of bandwidth, limiting it to a few hundred Hz, but making
analog better at random uncorrelated noise rejection. The Headsets inc
website posted the rejection capability of their system At low
frequencies it is about as good as the best digital system.

At high frequencies (above say 300 Hz), the passive rejection
capability of a good headset (mine is a David Clark H10-40) is more
than adequate to the task for my ears.

I've been trying to get HI interested in random motorcycle helmet noise
cancellation (generally under 100 Hz) but they don't seem interested -
or they may know why the analog control system can't be made stable.

>From my engineering experience, a 300 Hz analog response loop is an
impressive acheivement.

[Peter Duniho]

"nrp" > wrote in message
oups.com...
> On inquiry, I was told by technical people (I suspect it is a
> near-garage shop operation) at Headsets Inc that their rejection system
> is all analog.

So the answer to my question is "no", you do not have first-hand knowledge
of any headset that uses a predictive cancelling algorithm such as you
describe. Okay, thanks.

[Marc J. Zeitlin]

Peter Duniho wrote:

> So the answer to my question is "no", you do not have first-hand knowledge
> of any headset that uses a predictive cancelling algorithm such as you
> describe. Okay, thanks.

According to:

http://www.telex.com/aircraft/products.nsf/pages/Stratus50Digital

that's what they do. Never used one - I have no idea how well it
works, if at all. I have a Bose, a Lightspeed 15XL, and a Clarity Aloft.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2006

[nrp]

>So the answer to my question is "no", you do not have first-hand knowledge
of any headset that uses a predictive cancelling algorithm such as you
describe. Okay, thanks.<

I do have 25 years ystem engineering experience with error cancellation
techniques in the frequency domain.

[nrp]

>So the answer to my question is "no", you do not have first-hand knowledge

of any headset that uses a predictive cancelling algorithm such as you
describe. Okay, thanks.<

I do have 25 years of system engineering experience with error
cancellation
techniques in the frequency domain, as well as analog error
minimization techniques.

[Morgans[_4_]]

"Marc J. Zeitlin" > wrote

> According to:
>
> http://www.telex.com/aircraft/products.nsf/pages/Stratus50Digital
>
> that's what they do. Never used one - I have no idea how well it
> works, if at all. I have a Bose, a Lightspeed 15XL, and a Clarity Aloft.

Which is about what I was saying in my post, back a bit. I thought they all
worked that way, but I learned something new, in this thread.

I did not think that the electronic switching reactions to sound would be
quick enough to cancel a rising sound pressure, as it happens, by applying
an immediate 180 degree out of phase correction. I thought the correction
was applied to the next pulse, as it would happen, if it occurred again.
--
Jim in NC

[Roger[_4_]]

On 30 Aug 2006 12:10:35 -0700, "nrp" > wrote:

>Not all ANR headsets work on the same principle.
>
>I understand that most of them are digital, in that they look for
>repetitive noise & then use digital algorithims to s-l-o-w-l-y cancel
>out the repetitive components of any noise signal. This has the
>advantage that they can work to higher frequencies, but limited in that

But you don't need to have them work at higher frequencies and I
absolutely do not want them to work at higher frequencies. I can hear
the wind noise albeit weakly. I can hear the accessories on the
engine and I can hear voice through the set very well. Not too bad
even from some one beside me as the noise is only coming from one
direction and is not completely canceled by the ANR function.

>they only work with repetitive (i. e. cyclic) signals. They are unable
>to cancel random noise.

To me, those would be the ones to stay away from.
I see it as a case in simple is better.

>
>Some (the Headsets Inc version and maybe others) are a broad band
>analog bucking system. They do not cancel just a repetitive
>excitation, but can also cancel most of any random noise sensed by the
>internal microphone system. The disadvantage of this type is that it
>can work only at frequencies below typically about 300 Hz. Above this,

These including my Telex work very well up through the voice
frequencies. Don't believe what you hear about 300 Hz. If this were
true I'd hear a lot of prop noise at full RPM and I don't. After all
the prop makes more noise than anything else on, or in the plane. They
work well up to around 3000 Hz. At least all I've tried have.

>and they must rely on the passive noise rejection of the headset cups -
>which is pretty good at high frequencies. It is low frequencies that
>passive systems have the poorest atenuation.
>
>Anyone else with more of the puzzle?
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Roger (K8RI)]

On 30 Aug 2006 18:10:23 -0700, "nrp" > wrote:

>On inquiry, I was told by technical people (I suspect it is a
>near-garage shop operation) at Headsets Inc that their rejection system
>is all analog. Being somewhat familiar with analog and digital noise
>cancelling systems, I can verify that from the HInc system that I have.
> Oddly enough the final performance seems somewhat similar.
>
>It is easy to talk about a 180 degree cancelling pressure waveform
>generator (per Roger above), but that is an over-simplification of the
>problem that isn't acheiveable from a real control loop stability
>standpoint.

True it is a bit of an over simplification and it doesn't give the
ultimate noise cancellation of digital overall or predictive over
specific ranges.

OTOH it does work very well as any user who has turned off their
analog ANR while in flight and then turned them back on. The
difference is astounding and it is substantial so the analog phase
canceling works. Also this is not an area where you are looking for
control loop stability, but rater effectiveness and they are not the
same.

>
>Digital systems get around this by a slow optimization in the frequency

Remember the add hype and the claims that the new Telex has this
exclusively. We have to remember too that when you look at the
difference in db it doesn't appear much different. OTOH db is a ratio
and every 3 db is a doubling, or cutting in half depending on the
direction you are headed.

>domain over a wide (i. e. hi) frequency range at the expense of being
>able to cancel random noise, whereas analog does it in the time at the
>expense of bandwidth, limiting it to a few hundred Hz, but making

My day-to-day experience says the bandwidth limitation is not nearly
that drastic, but is on the order of one full magnitude wider at 3,000
Hz where the fall off becomes noticeable.

>analog better at random uncorrelated noise rejection. The Headsets inc
>website posted the rejection capability of their system At low
>frequencies it is about as good as the best digital system.
>
>At high frequencies (above say 300 Hz), the passive rejection
>capability of a good headset (mine is a David Clark H10-40) is more
>than adequate to the task for my ears.
>
>I've been trying to get HI interested in random motorcycle helmet noise
>cancellation (generally under 100 Hz) but they don't seem interested -
>or they may know why the analog control system can't be made stable.

A system that works on random noise by nature isn't stable, or we are
using the word differently. However a low frequency repetition rate
does not necessarily mean a low frequency sound. The bark of an
exhaust, supersonic prop tips, or a gun shot are all sounds with very
short rise times which makes them a high frequency sound, but with a
low repetition.

>>From my engineering experience, a 300 Hz analog response loop is an
>impressive acheivement.

They sure do a good job on that big Continental exhaust bark at low
RPM. All you hear are the accessories running.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com