Ear damage by MP3,DVD and digital TV? (risks of data reduction)

CYBERYOGI =CO= Windler windle_c at informatik.fh-hamburg.de
Thu Nov 28 23:35:58 EST 2002

Ear damage by MP3,DVD and digital television?
    -risks of neuroacoustically datareduced music

(A HTML version of this text with illustration diagrams can be found on my
   site at http://www.informatik.fh-hamburg.de/~windle_c/e_index.html       )

Nowadays technologies for lossy data compression of digital audio recordings get
widely used in more and more applications. This way methods like MP3, WMA, MPEG
and ATTRAC are not only used for memory saving music downloads through the
internet and comfortable use on portable players, but they are also employed for
background musics in modern videogames and already today they are used in
ordinary radio stations to store all kinds of audio material on harddisks to
permit comfortable access for broadcast. Due to such technologies are also
employed in DVD films and all other common digital video systems (those e.g. are
used for TV broadcasting), and because it is even planned to replace soon the
entire analogue television system with digital TV (DVB) that is based on these
technologies, it is strictly necessary to precisely research on the health risks
of modern data compression methods.

Unlike with compression and decompression of computer programs (e.g. ZIP), that
is to say, during lossy data compression (data reduction) the original signal is
not reconstructed 1:1, but to reduce the data amount, only control signals for a
synthesizer programs (called CODEC) get recorded, those are optimized in a way
that during rendition the CODEC can reconstruct from these an approximation of
the original picture or sound signal that appears as similar as possible for the
human conscious perception, but is not identical to the original signal. The
danger of this exploitation of human perception flaws is that especially by
lossy audio data compression sound portions get destroyed those, although the
brain would not pass them to the conscious awareness, are likely necessary for
the human hearing's own perpetual calibration.

The basic principle of modern audio data reduction is, that is to say, to omit
during storage exactly those sound portions those an average human being would
not consciously perceive. White science likes to call such methods gladly
playing down "psychoacoustic", although in fact they have really nothing to do
with psychology (the realization of sounds as pleasant or unpleasant etc.)
because their impact is on a far lower neurological level since they function on
a model of the cochlea in the human ear and thus need to be called correctly
"neuroacoustic" data reduction methods.

The cochlea
The cochlea ("snail") is the most important sound perception organ of humans. It
consists of a liquid filled, snail shaped, spiral- like rolled up, conical tube,
on which front end the sound waves are guided from the ear drum.

To distinguish sounds, the basilar membrane is stretched inside along the entire
tube, and at its full length their are hair- shaped, very sensitive sensor cells
attached to react on vibrations of the membrane. Depending upon the current
frequency portion, by resonance in the conical tube standing waves come into
being at different locations of the membrane, those thereby excite different
sensor cells to enable the brain to distinguish different sound pitches.

Because standing waves are not sharply focussed at one spot but always also
slightly excite membrane zones nearby, and because after a loud noise after-
vibrations (resounds) persist on the membrane for a short duration, the hearing
processor fields of the brain contain very finely co-ordinated compensation
circuits, those filter away all weak signals from these places because the side
resonances otherwise would occur in the conscious perception as annoyingly
roaring interference noises. Due to these compensation circuits it is generally
not possible for humans to consciously perceive quieter tones simultaneously or
briefly after loud tones at a frequency nearby, because they are filtered away
together with those unwanted interferences.

The lossy (neuroacoustic) audio data reduction does now basically nothing else
than to simulate the interferences of the cochlea and their compensation
circuits in the brain. For this it separates during recording the sounds by
filters into many frequency bands and evaluates for each band how strong its
perceptibility would be disturbed ("masked") by simultaneous or after- roaring
loud sounds on nearby frequency bands (i.e. basilar membrane zones). Then the as
best perceivable evaluated frequency bands get encoded with high sample
resolution, worse perceivable frequency bands with correspondingly lower sample
resolutions, and all sounds below a fixed threshold of perceptibility simply
don't get encoded at all but are omitted to save memory and transmission
bandwidth. During rendition the given samples are simply mixed together at their
corresponding frequency bands again, whereby all sound portions those were
omitted during recording stay naturally lost. Since the CODEC fools the hearing
processor fields of the human brain by its "hearing- correct" selection, this
way audio recordings can be reduced to less than 1/20 of their initial data
amount without a noticeable loss of much quality. But a continuous consumption
of datareduced audio could possibly lead to fatal consequences - this needs to
be estimated particularly critical in view to the planned replacement of the
analogue radio and television broadcast standards by digital successors (DAB, DVB).

Data reduction and DRM - a hazard for aural acuity?
The human hearing is an extremely finely co-ordinated cybernetic system, which
is in many respects superior in its efficiency to electronic noise recognition
systems - so it e.g. can successfully listen to a single voice among background
noises and many simultaneous discussions, which even the most advanced manmade
machines still can't compete. Like most biological systems it depends however
for this on perpetual calibration by external signals (exactly like our speech
ability, which as well known after deafness degenerates horribly fast into
hardly understandable mumbling). Also the compensation circuits against the
resonance interferences of the cochlea therefore require most likely for correct
function continual calibration by a variety of naturally built up noises.

  From the view of neuronomy it is therefore to classify, although not as acutely
dangerous, at least as very precarious that a wider and wider spreading audio
transmission technology for data reduction just systematically removes those
spectral sound portions at the auditory threshold, on those normally the hearing
processor fields of our brain decide whether they shall be perceived or filtered
out, because so the signal for their self calibration is missing, whereby at
longer term a maladjustment of the hearing processor fields can threaten.
Possible consequences of intensive consumption of datareduced audio material
could therefore include ear noises (tinitus), a general degradation of the
perception of quiet sounds, as well as a worsened timbre perception  (a
so-called "tin ear"), which would make the human of the cyberage even more
insensitive than he already yet has become by the continuous mass media
infotrash bombardment he is exposed to. Actually it is still unclear whether the
consequences of such maladjustments are only temporary (similarly like seeing
the world in green/ red discoloured after taking off red/ green 3D glasses) or
if the continuous consumption of neuroacoustically datareduced sounds can lead
to long lasting or even permanent damage.

A possible advantage of the data reduction characteristic to remove all sound
portions classified as "inaudible" could however even be that one could clean
with it supposingly contaminated audio material (as for instance propaganda from
dictatorships) from so-called subliminals (i.e. hidden hypnotic suggestion
messages those are intended to get into the brain without getting into conscious
awareness) before listening. The sound carrier industry plans however with their
DRM campaign (digital rights management) to mix into any commercially
distributed audio recordings so-called "digital watermarks", those as an
artificial and likewise allegedly not consciously audible sound portion shall
contain digitally readable copyright information those besides copying onto
analogue cassettes shall even survive the mentioned neuroacoustic data
reduction. How a so persistent, artificial signal that repeats over the entire
length of an recording affects brain and hearing is very uncertain, and I expect
that at least the sound quality will degrade from it (much like with those
artificial press faults on some "copy protected" audio CDs, those actually
violate the "Red Book" standard for CDs and already therefore don't belong into
commerce since these constitute defective products declared as audio CDs).

I personally own mainly cheap CDs and phono records, but almost no downloaded
MP3 musics. I have however some computer games with MP3 music, but I don't
excessively play them. Despite I listen to music only quietly, I have repeatedly
tinitus (and thus I also suspect the data reduction in radio and TV broadcasts
as a cause). Nevertheless I try here in no way to demonize MP3 in the name of
the sound carrier industry, because most music CDs are definitely 2 to 4 times
overpriced and everybody  who practices by downloading private "self law"
against the sound carrier industry has my solidarity. In principle I find the
possibilities of data reduction even very good, because it makes the system of
music publishing more democratic, since by the internet now also hobby musicians
so finally get a chance to spread their works world- wide. Even myself however
would by my current knowledge still dare to publish sometime composed music
pieces by me on the internet using MP3 or Vorbis/ Ogg data reduction (but with a
warning hint not to listen to them excessively). In spite of this I consider the
negligently increasing spread of neuroacoustic data reduction critical, since
nobody has yet analyzed the health consequences, and of all by the nationally
planned introduction as new TV and radio broadcast standards a future avoidance
will become almost impossible. Also the more and more increasing rate of hearing
damages with young people could not only originate by the volume, but partly
also by the data reduction employed in the musics they consume.

Possibly the hazards could be reduced already by improving the CODECs in such a
way that they replace during rendition the omitted spectral sound portions by
synthetically computed portions to emulate the spectral behaviour of natural
noises well enough for the calibration of the hearing processor fields. But here
definitely exists acute research need, therefore I request hereby all
politicians and neuroacoustics scientists to be concerned with the danger
potential of neuroacoustic data reduction and to postpone the abolishment of the
analogue radio and TV standards until all risks have been clarified.

                          MAY THE SOFTWARE BE WITH YOU!

I                  CYBERYOGI Christian Oliver(=CO=) Windler                  I
I         (teachmaster of LOGOLOGIE - the first cyberage-religion!)          I
I                                      !                                     I

More information about the Neur-sci mailing list