[Harlan Messinger]

I've got a pair of Sony MDR-NC6 noise-canceling headphones. They do a
great job of removing the low, rumbling sounds, like the office copier
or the continuous roar on a plane. On the other hand, on a plane, they
do virtually nothing about the higher-frequency airplane sounds
(hissing, whining), and they add their own hiss.

I asked someone selling expensive Bose headphones at Denver Airport
about whether their phones cover the higher frequency ranges, but he
turned out not to be informed on such a technical topic.

Is this issue with my Sony phones normal--are only the lower frequencies
targeted by today's noise-canceling products? Or are there products that
I can rely on to cancel a wider range of frequencies and, ideally don't
introduce significant noise of their own?

[Don Pearce[_3_]]

On Thu, 04 Jun 2009 13:04:08 -0400, Harlan Messinger
wrote:

I've got a pair of Sony MDR-NC6 noise-canceling headphones. They do a
great job of removing the low, rumbling sounds, like the office copier
or the continuous roar on a plane. On the other hand, on a plane, they
do virtually nothing about the higher-frequency airplane sounds
(hissing, whining), and they add their own hiss.

I asked someone selling expensive Bose headphones at Denver Airport
about whether their phones cover the higher frequency ranges, but he
turned out not to be informed on such a technical topic.

Is this issue with my Sony phones normal--are only the lower frequencies
targeted by today's noise-canceling products? Or are there products that
I can rely on to cancel a wider range of frequencies and, ideally don't
introduce significant noise of their own?

It is not a case of low frequencies being targeted, but really that
dealing with high frequencies is much more technically challenging. If
you really want good HF isolation, forget noise cancelling and buy
some passive ear defender types.

d

[Harlan Messinger]

Don Pearce wrote:
On Thu, 04 Jun 2009 13:04:08 -0400, Harlan Messinger
wrote:

I've got a pair of Sony MDR-NC6 noise-canceling headphones. They do a
great job of removing the low, rumbling sounds, like the office copier
or the continuous roar on a plane. On the other hand, on a plane, they
do virtually nothing about the higher-frequency airplane sounds
(hissing, whining), and they add their own hiss.

I asked someone selling expensive Bose headphones at Denver Airport
about whether their phones cover the higher frequency ranges, but he
turned out not to be informed on such a technical topic.

Is this issue with my Sony phones normal--are only the lower frequencies
targeted by today's noise-canceling products? Or are there products that
I can rely on to cancel a wider range of frequencies and, ideally don't
introduce significant noise of their own?

It is not a case of low frequencies being targeted, but really that
dealing with high frequencies is much more technically challenging. If
you really want good HF isolation, forget noise cancelling and buy
some passive ear defender types.

Really, it's more challenging? I would have thought one approach would
be applicable across the spectrum. Do you know of any resources I can
look at that will explain the technical details? Meanwhile, thanks for
the tip.

[Richard Crowley]

"Harlan Messinger" wrote ...
Don Pearce wrote:
It is not a case of low frequencies being targeted, but really that
dealing with high frequencies is much more technically challenging. If
you really want good HF isolation, forget noise cancelling and buy
some passive ear defender types.

Really, it's more challenging? I would have thought one approach would be
applicable across the spectrum.

The fundamental theory is the same. But reconstructing a cancellation
signal at higher frequencies requires more processing horespower
(i.e. faster processors). And at shorter wavelengths it gets trickier
to deliver the exact cancellation waveform *at your eardrum* from
several mm away.

As Mr. Pearce suggests, passive isolation is still the more practical
way of dealing with HF noise toay.

[[email protected]]

On Jun 4, 1:32*pm, "Richard Crowley" wrote:
"Harlan Messinger" wrote ...

Don Pearce wrote:
It is not a case of low frequencies being targeted, but really that
dealing with high frequencies is much more technically challenging. If
you really want good HF isolation, forget noise cancelling and buy
some passive ear defender types.

Really, it's more challenging? I would have thought one approach would be
applicable across the spectrum.

The fundamental theory is the same. But reconstructing
a cancellation signal at higher frequencies requires
more processing horespower (i.e. faster processors).

More "horsepower?" In the limiting case, all the
horsepower that's needed is inverting the phase
of the signal.

And at shorter wavelengths it gets trickier
to deliver the exact cancellation waveform
*at your eardrum* from several mm away.

THAT'S the crux of the problem: the fact that
the microphone used to detect the original
noise signal and the transducer used to produce
the cancelling signal can not physically occupy
the same point. Further, the REAL point where
you want the cancellation to occur is in the ear
canal, where it is, at best, very inconvenient to
place either.

It works well at low frequencies because the
wavelengths are large (at 100 Hz, they're 11 feet
long), thus the difference in sound pressure between
the microphone and cancelling speaker (say they're
two inches apart) is small and the phase difference
is also small (on the order of about 6 degrees).

At 10 kHz, those wavelengths are on the order of
1.4 inches of an inches, substantially larger than
our hypothetical 2" separation.

[Richard Crowley]

dpierce wrote ...
"Richard Crowley" wrote:
The fundamental theory is the same. But reconstructing
a cancellation signal at higher frequencies requires
more processing horespower (i.e. faster processors).

More "horsepower?" In the limiting case, all the
horsepower that's needed is inverting the phase
of the signal.

At what sampling rate?

[Don Pearce[_3_]]

On Thu, 04 Jun 2009 13:25:42 -0400, Harlan Messinger
wrote:

Don Pearce wrote:
On Thu, 04 Jun 2009 13:04:08 -0400, Harlan Messinger
wrote:

I've got a pair of Sony MDR-NC6 noise-canceling headphones. They do a
great job of removing the low, rumbling sounds, like the office copier
or the continuous roar on a plane. On the other hand, on a plane, they
do virtually nothing about the higher-frequency airplane sounds
(hissing, whining), and they add their own hiss.

I asked someone selling expensive Bose headphones at Denver Airport
about whether their phones cover the higher frequency ranges, but he
turned out not to be informed on such a technical topic.

Is this issue with my Sony phones normal--are only the lower frequencies
targeted by today's noise-canceling products? Or are there products that
I can rely on to cancel a wider range of frequencies and, ideally don't
introduce significant noise of their own?

It is not a case of low frequencies being targeted, but really that
dealing with high frequencies is much more technically challenging. If
you really want good HF isolation, forget noise cancelling and buy
some passive ear defender types.

Really, it's more challenging? I would have thought one approach would
be applicable across the spectrum. Do you know of any resources I can
look at that will explain the technical details? Meanwhile, thanks for
the tip.

No need, I can explain. It is all a matter of wavelength. Outside the
headshell is a microphone that picks up the environmental sound which
must be suppressed. An inverted version of that sound is played inside
the headphones along with the wanted signal. The idea is that the
inverted sound cancels out the actual sound. For low frequencies it
works nicely, because the inverted and direct sounds line up nicely.
But at higher frequencies the wavelength becomes sufficiently small
that alignment becomes impossible, For example at 10kHz the wavelength
is about one inch, so if the microphone is half an inch from the
speaker (almost inevitable), there will be a half wave error, and far
from cancelling the sound will actually reinforce. Below 10kHz, the
situation is not that bad, but bad enough that good cancellation is
impossible.

d

[Mr.T]

"Don Pearce" wrote in message
news:4a2c020b.558504156@localhost...
On Thu, 04 Jun 2009 13:04:08 -0400, Harlan Messinger
wrote:

I've got a pair of Sony MDR-NC6 noise-canceling headphones. They do a
great job of removing the low, rumbling sounds, like the office copier
or the continuous roar on a plane. On the other hand, on a plane, they
do virtually nothing about the higher-frequency airplane sounds
(hissing, whining), and they add their own hiss.

I asked someone selling expensive Bose headphones at Denver Airport
about whether their phones cover the higher frequency ranges, but he
turned out not to be informed on such a technical topic.

Is this issue with my Sony phones normal--are only the lower frequencies
targeted by today's noise-canceling products? Or are there products that
I can rely on to cancel a wider range of frequencies and, ideally don't
introduce significant noise of their own?

It is not a case of low frequencies being targeted, but really that
dealing with high frequencies is much more technically challenging. If
you really want good HF isolation, forget noise cancelling and buy
some passive ear defender types.


I don't own any NC headphones, but surely anything designed properly, rather
than just for marketing hype, would use a combination of both NC to combat
LF noise where simple isolation is difficult and less affective, and use
good insulation/isolation of the higher frequencies where NC is impossible.

I imagine there are some that do meet the criteria, but you may need to look
past Sony and Bose, and put up with bigger, heavier headphones.

MrT.

[Don Pearce[_3_]]

On Fri, 5 Jun 2009 14:55:55 +1000, "Mr.T" MrT@home wrote:


"Don Pearce" wrote in message
news:4a2c020b.558504156@localhost...
On Thu, 04 Jun 2009 13:04:08 -0400, Harlan Messinger
wrote:

I've got a pair of Sony MDR-NC6 noise-canceling headphones. They do a
great job of removing the low, rumbling sounds, like the office copier
or the continuous roar on a plane. On the other hand, on a plane, they
do virtually nothing about the higher-frequency airplane sounds
(hissing, whining), and they add their own hiss.

I asked someone selling expensive Bose headphones at Denver Airport
about whether their phones cover the higher frequency ranges, but he
turned out not to be informed on such a technical topic.

Is this issue with my Sony phones normal--are only the lower frequencies
targeted by today's noise-canceling products? Or are there products that
I can rely on to cancel a wider range of frequencies and, ideally don't
introduce significant noise of their own?

It is not a case of low frequencies being targeted, but really that
dealing with high frequencies is much more technically challenging. If
you really want good HF isolation, forget noise cancelling and buy
some passive ear defender types.


I don't own any NC headphones, but surely anything designed properly, rather
than just for marketing hype, would use a combination of both NC to combat
LF noise where simple isolation is difficult and less affective, and use
good insulation/isolation of the higher frequencies where NC is impossible.

I imagine there are some that do meet the criteria, but you may need to look
past Sony and Bose, and put up with bigger, heavier headphones.

MrT.


Phones that isolate the HF well also tend to deal with the bottom end
without resort to active cancelling. Where active phones work well is
in situations like light aircraft where there is a great deal of throb
and drone to get rid of, which is well taken care of with FFTs and
multiple band generators. Then, because the headshells are lightweight
and not particularly padded, all the other external sounds that you do
want to hear - radios, beacons, your passenger etc, which are not
repetitive - are far better heard than without them. That, as far as I
can see, is the true raison d'etre for active phones.

d

[Mr.T]

"Don Pearce" wrote in message
news:4a2fb739.604885062@localhost...
Phones that isolate the HF well also tend to deal with the bottom end
without resort to active cancelling.

Not so, LF is a lot harder to absorb than HF.

Where active phones work well is
in situations like light aircraft where there is a great deal of throb
and drone to get rid of,

That *is* LF noise, and the main reason for NC headphones. The OP wanted
more HF reduction as well, which is beyond the scope of active NC without
placing your head is a vice!

Then, because the headshells are lightweight
and not particularly padded, all the other external sounds that you do
want to hear - radios, beacons, your passenger etc, which are not
repetitive - are far better heard than without them. That, as far as I
can see, is the true raison d'etre for active phones.

That may be so for some, IF the manufacturers made that clear to the buyers.
Personally I'd want ones that block LF *and* HF however, which appears to be
what the OP wants as well.

MrT.
..

[Don Pearce[_3_]]

On Fri, 5 Jun 2009 20:02:27 +1000, "Mr.T" MrT@home wrote:


"Don Pearce" wrote in message
news:4a2fb739.604885062@localhost...
Phones that isolate the HF well also tend to deal with the bottom end
without resort to active cancelling.

Not so, LF is a lot harder to absorb than HF.

You don't absorb it, you block it, which is not the same. Stiffness
and a bit of mass does the job.

Where active phones work well is
in situations like light aircraft where there is a great deal of throb
and drone to get rid of,

That *is* LF noise, and the main reason for NC headphones. The OP wanted
more HF reduction as well, which is beyond the scope of active NC without
placing your head is a vice!


I already went through that in my first post.

Then, because the headshells are lightweight
and not particularly padded, all the other external sounds that you do
want to hear - radios, beacons, your passenger etc, which are not
repetitive - are far better heard than without them. That, as far as I
can see, is the true raison d'etre for active phones.

That may be so for some, IF the manufacturers made that clear to the buyers.
Personally I'd want ones that block LF *and* HF however, which appears to be
what the OP wants as well.

Yup, that has been dealt with to the OP's satisfaction - we've moved
on to another facet now. It isn't an LF/HF thing. It is a
repetitive/non-repetitive differentiation. You need to hear the
one-off events while blocking the background drone. That is where NC
phones score over block-everything passives.

d