Monday, September 29, 2008

Sounds Above 20,000 Hz: Are They Important to Audiophiles?

Even though a disparagingly large number of people say that only dogs or bats care about sounds about 20,000 Hertz, but is there any truth in this? Does ultrasonic sound belong in hi-fi?

By: Vanessa Uy

Dogs, bats, and those “10-year old Classical Music w√ľnderkinder” are probably the least-explored and exploited high-end audio market on Earth. And yet nobody ever – not even the multinational consumer electronic manufacturers – admit on the mainstream press about how difficult it is to digitally record sound waves with frequencies above 20,000 Hertz. Despite of over 15 years worth of anecdotal evidence among the hi-fi community that sounds above the “supposedly 20 thousand Hertz human audibility limit” or ultrasonic frequency sounds indeed has a bearing on sound quality.

Despite of a widely publicized (or is that declassified?) during the 1990’s US Army research on psycho-acoustics that identified parts of the inner ear capable of detecting airborne sound waves at 80,000 Hertz (four times the oft accepted 20,000 Hertz limit). Many of the biggest sound-equipment manufacturers still kept assuring their customers that sounds with frequencies above our threshold of hearing is of no consequence to their product’s sound quality. But we the audiophile community soldiered on. We even experimented with piezoelectric supertweeters capable of producing airborne sound waves above 20,000 Hertz.

Technically, the problem of digitally recording sound waves with a degree of faithfulness to the original sound or fidelity is no way much easier than the analog recording systems of yore that digital recording intends to replace. Even standard compact discs whose highest frequencies reach only 22,050 Hertz and yet it requires almost 800 megabytes of storage space to save 80 minutes worth of music. SACD s and other high-resolution audio formats whose frequency bandwidth are twice to five times that of redbook CD requires four times the data space, which necessitates the use of a visible-light red laser for playback. Despite the state-of-the-art sound quality and technical tour de force most high-resolution digital music formats have been relegated to the curiosity museum; Either due to lack of promotion or fear of music piracy. Isn’t the cause of music piracy is that the non-audiophiles – i.e. 99.9999% of the population – has wholeheartedly adopted the good enough mentality when it comes to sound quality?

Another problem of the quality improvement in wide-bandwidth digital audio is that most of the sound quality improvement occurs far from the frequency of interest, like SACD s and DVD-Audio recordings of purist acoustic Classical and Jazz music are often praised by audiophiles for their grain-free midrange frequencies and tight bass. Only on music that contains strongly struck cymbals like Heavy Metal Rock Music reissues is the improvement on high-frequency reproduction is noted during listening sessions.

To me, the hi-fi industry today – especially those that are just mere subsidiaries of gigantic consumer electronic companies – will forever be reluctant to promote the concept of audio systems. Especially those capable of faithfully reproducing sounds above 20,000 Hertz because kids, teen-age girls, dogs, bats or anyone with ultrasonic hearing are not so willing to pay the seven digit telephone-number price tags these high-ticket items are likely to be priced. It is one of Mother Nature’s ultimate act of cruelty, by the time you can afford the audio system of your dreams the onset of age-related hearing loss starts to manifest itself. So say goodbye to ultrasonic hearing. Especially once you’ve reached the wrong side of thirty, and no your Veruca Salt CD s are not getting worn down or getting to sound duller.

1 comment:

Girlie May said...

I think audio engineers who cared about sound quality were aware of this phenomena during the middle of the 1990s. I think there was a heated discussion during the development of Pacific Microsonics' HDCD system about how sounds we cannot hear - especially those above 20,000 Hz in frequency - can affect the sounds we can here. Which manifests itself as mid-range sound quality.