You are reading the older HTML site

Positive Feedback ISSUE 52
november/december 2010


Are Ultrasonics Important? Current Theory and High Resolution Digital
by Teresa Goodwin


The ultrasonic frequency controversy...

Ultrasonic frequencies are said to affect the sound of the audible frequencies we hear. According to these theories ultrasonics are not heard as "normal" sound but processed by our brains and some believe the nerve endings on our skin. That is what they claim makes live music feel and sound live due to the natural ultrasonics of real musical instruments. Even people with severe hearing loss in the audible range, are said to still experience ultrasonics.

Ultrasonic hearing research to help deaf people hear

Research is ongoing in shifting frequencies in the normal audible range (20-20 kHz) to the ultrasonic range so they are perceived by the severely and profoundly deaf who are not helped by other methods.

Human Ultrasonic Hearing

"Scientists since 1954 have known of the capability of humans to hear ultrasonic frequencies (23,000 - 100,000Hz.). The only problems has been : 1) Up-shifting audio sound cleanly to ultrasound (for speech comprehensibility); and 2) delivering the ultrasound to the body. I have spent the last 5 years developing a portable device which addresses and handles these problems. The technology has been tested on severely and profoundly deaf adults and children (as well as normal hearing individuals) with excellent results. Conversational speech as well as music is easily heard and understood. This is a noninvasive approach and thus offers a viable alternative to the cochlea implant procedure. I thought it was time to let the news out."

Ultrasonic hearing research from Wikipedia

"Ultrasonic hearing is a recognized auditory effect which allows humans to perceive sounds of a much higher frequency than would ordinarily be audible using the physical inner ear, usually by stimulation of the base of the cochlea through bone induction. Human hearing is recognized as having an upper bound around 17-20 kHz, depending on the person, but ultrasonic sinusoids as high as 120 kHz have been reported as successfully perceived.

Two competing theories are proposed to explain this effect. The first asserts that ultrasonic sounds excite the inner hair cells of the cochlea basal turn, which are responsive to high frequency sounds. The second proposes that ultrasonic signals resonate the brain and are modulated down to frequencies that the cochlea can then detect. Researchers Tsutomu Oohashi et. al. have coined the term hypersonic effect to describe the results of their controversial study supporting audibility of ultrasonics.

By modulating speech signals onto an ultrasonic carrier, intelligible speech has also been perceived with a high degree of clarity, especially in areas of high ambient noise. B. Deatherage states that what humans experience as ultrasonic perception may have been a necessary precursor in the evolution of echolocation in marine mammals."

The role of ultrasonic frequencies

Ultrasonic frequencies are not heard as sound but said to be processed by the brain, possibly bone conducted. Everyone no matter how severe their hearing losses are in the audible range respond to ultrasonic frequencies. Most people are familiar with how we respond to inaudible bass frequencies such as the 16 Hz organ note at the opening of Also Sprach Zarathustra, we only hear the overtones as humans cannot actually "hear" the 16Hz fundamental, but we feel the 16Hz in our bones. Take away the 16 Hz tone and you take away the notes power.

Ultrasonics are processed much the same as subsonics, we feel them on our skin and our brain processes them.

I have known of and realized the benefit of ultrasonic frequencies for over 25 years. They make a big difference in the liveliness and realism of music especially in the "feeling" of being in the presence of real live musicians. After going to a full range system where frequencies extend up to 45kHz, I would never go back to one limited to only 20kHz!

My preamp's frequency response extends to 80kHz, my power amp to 100kHz, and my speakers to 45kHz. Even when I listen through my Sennheiser headphones the frequency response extends to 35kHz.

I think ultrasonics are the "something missing" I always notice when listening to CDs, that is the ones that are not unpleasant to hear. Which is the other reason I have never taken to CDs, LPs have frequency response up to 35 kHz from tape and up to 50 kHz if recorded Direct to Disc. I used to have the Alpha Genesis 1000II Moving Coil Cartridge the frequency response was 10-75kHz +/- 1dB, so SACD was not the first ultrasonic format I've owned. Indeed even before SACDs there was 24 Bit 96 kHz DVD DADs from Chesky, Classic Records, and a few others. Even those show how poor 44.1kHz PCM and CD is by comparison.

Why anyone would record music where frequency response and resolution are limited to 20 kHz and 44.1 kHz PCM is just one of many enigmas that I can't comprehend. Musical Instruments have overtones extending to 102.4 kHz. There's Life Above 20 Kilohertz!

A Survey of Musical Instrument Spectra to 102.4 kHz

SACDs that use the full resolution available with DSD

The frequency response of SACDs can go out to 100 kHz although only a few microphones go out the far. One such microphone is the Sanken CO-100K which the last Telarc SACDs used for the main orchestra pickup. 

John Adams: On the Transmigration of Souls - Robert Spano/Atlanta Symphony Orchestra & Chorus [Telarc SACD-60673]

Britannia - Donald Runnicles/Atlanta Symphony Orchestra [Telarc SACD-60677]

Michael Gandolfi: The Garden of Cosmic Speculation - Robert Spano/Atlanta Symphony Orchestra [Telarc SACD-60696]

Puccinni: La Boheme - Robert Spano/Atlanta Symphony Orchestra & Chorus and Guests [Telarc SACD-60697 (2 discs)]

Mussorgsky: Pictures at an Exhibition, "Night on Bald Mountain, Prelude to Khovanshchina" - Paavo Jarvi/Cincinnati Symphony Orchestra [Telarc SACD-60705]

It is too bad that Concord Music Group ended the Telarc SACD program a year and a half ago as Telarc still records DSD in stereo and multi-channel, using Sanken CO-100K microphones. Most of the DSD recorded SACDs sound superb, very realistic, and natural however this microphone took their recordings to a new higher level.

We need New Rock and Jazz SACDs using the Sanken CO-100K microphone

I believe Rock and Jazz SACDs made to the highest audiophile standards would show off the SACD format to its best advantage as high percussion instruments have the highest ratio of ultrasonic to audible frequencies.

For example, the proportion of energy above 20 kHz is:

Muted trumpet, 2 percent (harmonics extend to 80 kHz)

Violin, 0.04 percent (harmonics extend to above 40 kHz)

Oboe, 0.01 percent (harmonics extend to above 40 kHz)

Cymbals, 40 percent (harmonics still strong at 100 kHz) 

Muted trumpets are used a lot in Jazz, and cymbals are heavily used in both Jazz and Rock. While percussive rich Classical music recorded in a concert hall does have a lot of ultrasonic energy, I do not believe it can compete with Jazz and Rock with the percentage of ultrasonic to audible frequencies. This explains why I usually pull out a Jazz SACD to show off the sonic advantages of the format. I never knew why I did that, now I have scientific proof for my choices in demo material. 

If we could get the engineers of all the new Pop, Rock, Rap, and Hip-Hop music to record DSD and use microphones that reach to 100 kHz then I believe SACD will hit the mainstream and then and only then will it replace the CD format.

For my opinions on Rock and Jazz music already recorded see "SACD Reviews, News, Views and Another Recommended Tweak - PART THREE: The case for Rock and Jazz SACDs"

Other high resolution digital 

To really appreciate any high resolution music on any format, look for music recorded in a real live acoustic space such as a concert hall, jazz club, or church.  Look for pure DSD, high resolution PCM or high quality analog masters especially from "audiophile" companies.

With high resolution downloads, confirm that the music file is native 24/88.2 or higher and not upsampled.

Ultrasonics in analog media

What's Going On Up There?

"Finally, it gives me a new respect for the venerable analog medium: Many of the recordings I looked at that turned out to have significant ultrasonic content were originally recorded on analog tape."óJohn Atkinson.

The final step: a Full Frequency audio system

One needs a full frequency system to hear the gigantic improvement true high resolution brings to digital sound. My Infinity Kappa 7 Reference speakers are flat to within 3dB to 45kHz, my tube preamp to 80kHz and my power amp to 100kHz, so I am reproducing ultrasonics from high resolution sources up to 45kHz. That makes me wonder how SACDs, DVD-Audios and high resolution downloads sound on frequency response limited systems that cannot reproduce their ultrasonics. I suspect that many who claim there is no sonic difference between high resolution formats and CD have at least one component in their reproduction chain that is limited to 20kHz, thus degrading all formats to no better that CD resolution.

Your DVD-Audio or universal player should be set to "Audio Direct" as should any SACD player which is also a DVD-Video player. This gives the most direct path and bypasses the video circuitry. In addition, the display should be turned off to eliminate LCD noise entering the signal path and to keep you from being distracted from the music by watching your player count time.

Your high resolution player should be plugged directly into a pre-amp, integrated-amp, or receiver that allows a "pure analog" direct sound path that bypasses all equalization and other signal altering devices. Basically all you want is a direct straight wire with gain path from the high resolution player to speakers with the widest frequency response possible. 

Lastly beware of receivers with DSP (Digital Signal Processing). Many stereo and multi-channel receiver/preamplifiers provide stereo and/or multi-channel analog inputs that are routed to analog-to-digital PCM converters for Digital Signal Processing control, often at 44.1kHz. The signals are then passed on to digital-to analog converters for the final output to speakers. This "feature" will cause ALL signals, regardless of source, to be no better quality than that of CD playback. Considering that you are playing a high resolution source with a sampling rate many orders of magnitude greater than that of CD, use a receiver or preamplifier that passes the stereo and/or multi-channel analog signals through entirely in the analog domain. Keeping the signal in analog, without any further digital inter-steps, will insure you will be enjoying the full quality of all high resolution sources. All "effects" programs should be disabled, such as "concert hall", "stadium", "nightclub", etc. These ambience programs, which are more suitable for home video use, will destroy the carefully mixed 2 channel stereo and multi-channel surround presentation you will find on high resolution sources.

Deep Listening: Why Audio Quality Matters

Participants: Steve Berkowitz, Greg Calbi (moderator), Evan Cornog, Michael Fremer, Kevin Killen, Craig Street

The panelists in Deep Listening: Why Audio Quality Matters confirmed almost everything I've been saying for years and even made the prospects for industry wide high resolutions downloads look like a very cheery possibility as computer memory and bandwidth increases.

Here are some of my favorite highlights:

'Super Audio CD was the closest we ever had to the master tape and what did we do? We buried it.'

'I never thought 16 bit 44k was good enough.'

'SACD is so many orders of magnitudes better than CD." (Unanimous agreement for the panelists.)

"I agree with you Redbook has always sounded awful."

"192kHz master downgraded to Redbook was awful."

"The removal of frequencies above 20 Hz is what causes the irritation we hear in Redbook CDs as we are not feeling the music through our skin.... One of the reasons we do other things when we listen to CDs, whereas LPs cause us to sit down and listen."

This was long and I didn't get everything but it was described how feeling the music though our bodies was even more important than what we actually hear through our ears, including subsonic and ultrasonic frequencies.

"Apple will introduce kids to high resolution. As memory increases the kids will be introduced to high resolution with free music tracks, first by hearing lossless and then high resolution."

I really did enjoy this round table discussion.

Ultrasonic Noise

No discussion of Ultrasonics would be complete without touching on ultrasonic noise in the DSD system. SACD detractors use this to discredit and denounce the format.

Could ultrasonic noise in DSD be related to its smooth and more relaxing sound quality? Dither is basically analog noise added to a PCM digital signal to smooth it out. ( So noise in itself can in some cases be helpful and not the evil thing many believe it to be.

One bit DSD generates a lot of noise and it is shifted upward to the ultrasonic frequencies where it would not be heard as noise. The theory is that ultrasonic frequencies effect the audible frequencies making them more timbre accurate and the music and performance space sound more live. In addition to the theories on how we perceive inaudible ultrasonic frequencies and how our brain processes them, does this ultrasonic noise affect the audible frequencies as well by making them smoother, more relaxing and more enjoyable?

If engineers were able to completely remove this ultrasonic noise will they also be removing the "magic" that makes SACD so smooth and analog-like?