I found this bit in the "New Car Features" PDF and thought some people might find it interesting

Psychoacoustic Theory:

Psychoacoustic theory is technology that exploits human perceptions (sensory illusions). Through the implementation of this technology, without changing the speaker sizes or locations, listeners can sense deeper bass sound (1) and feel as if the speakers were located at eye level, despite them being located in low positions like door speakers (2).

(1) Bass Sound Reproduction Principle: Since olden times, when pipe organs are built in churches, due to the difficulty of housing long resonating pipes for very low tones, a technique has been used which reproduces low tones through the utilization of two short pipes.

When two pipes, of which the frequencies are 100 Hz and 150 Hz, are sounded simultaneously to
reproduce a note at 50 Hz, human brains discern four different notes at 100 Hz, 150 Hz, 250 Hz (100 Hz + 150 Hz) and 50 Hz (150 Hz - 100 Hz). Among these, human brains perceive the frequency difference of 50 Hz most strongly.

By electrically generating differential components from fundamental notes for very low tones and emitting them through speakers, the human brains sense the deep bass sound despite it being not emanated from the speakers.

(2) Virtual Sound Source Layout: When the theory of HRTFs (Head Related Transfer Functions) is employed in the vertical direction, human brains perceive the source of sounds emitted from the speakers in the lower positions as if it was at windshield level.

HRTFs are acoustic transfer functions from the sound source to the ears. It is said that humans detect the location of sound sources through time differences and physical reflective interference; the horizontal direction is recognized through the time difference between the sound reception of the left and right ears, and the vertical direction is discerned through the reflective interference caused by the head and earlobes.

Sound sources can be virtually reproduced by incorporating the HRTFs into amplifiers and emitting the sound through speakers.

 

Cool, thank you! I was pondering how I got the low bass response without the big subwoofer. Makes sense.

Robb

 

So thats why my car vibrates when the stereo is crankesd

 

Tideland Prius — It's interesting that the Psychoacoustic Theory you quoted from the non-hybrid version of the "New Car Features Guide" does not appear in the hybrid version! I have done some experiments on my TCH's JBL system, and I don't believe that Toyota have actually implemented either of these "features." Note that the JBL amplifier is identical in both of the hybrid and non-hybrid vehicles.

1. Using pure tones down to below 30 Hz, I am unable to detect any sign of an attempt to create a "synthetic fundamental." The fundamental frequencies in the low-frequency range are genuine and pure. (The description given also is questionable.)
2. Careful listening tests with one-third-octave bands of noise show that the acoustical crossover frequency between the front woofers (in the front doors) and tweeters (in the dashboard near the windshield) occurs between 300 and 400 Hz. This means that musical frequencies lower than ~300 Hz come mainly from the woofers in the front doors, while frequencies higher than ~400 Hz come mainly from the tweeters by the windshield. Now, the Head Related Transfer Function (HRTF) method of elevating sounds only works in the frequency range where the outer ears ("pinnae") are effective, which is above ~1 kHz. Since all frequencies above 1 kHz come from the tweeters by the windshield, they don't need "elevating" (if they came from the door speaker that might have been a good idea).

So, I conclude that the JBL amplifier is not applying this processing to the sound, and I'm glad about this. I wonder why this irrelevant "theory" made its way into the non-hybrid Guide?

Stan

 

I agree that the analogy to the synthetic fundamental generated by pipe organs is vacuous. While the pipe organ has separate pipes for each note (and pipes that generate second and third harmonics can be easily built for each), the audio system must reproduce complex combinations of sounds at different frequencies. Not only would the extreme harmonic distortion of single tones be unacceptable, but the any combination of tones would generate such severe intermodulation distortion as to be rendered as "noise". No wonder they don't implement it. I'd say Toyota's Marketing department went way out on a limb with this one!

 

Actually, most of the pipe organs I've seen (...don't ask) have used a cap technique. For example. you take a 16 foot pipe and cap the top to create the equivalent of the a 32 foot pipe (one octave lower). The air has to travel up then down, so travels twice the distance.

In fact, while they do exist, I've personally never seen a "real" (sometimes called "full length") 64' Diaphone's. They have always been capped 32 foot pipes.

......not sure how I relate any of this information to my car mind you....

Later!

Dang

 

So there are two JBL audio systems - XLE/SE and the Hybrid one?

 

Sure. "stopped" versus "open" pipes. The synthesized approach saves space and money by not needing the pipes at all. It allows having a 16' rank of pipes for the pedal on a small organ with only 8' ranks by coupling in ranks at unison and a fifth higher. Pretty klunky, and not something I'd advertise as a great feature in a premium car stereo system!
Well, exhaust pipes are tuned!

 

Tideland Prius — Sorry if I was unclear. No, there is just the one JBL audio system in the 2007/8 Camry's. The Hybrid's system is the same as the one in the XLE/SE.

Stan

 

oh and it doesn't have psychoacoustics? despite the claims?