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.
<div class='quotetop'>QUOTE(Tideland Prius @ Nov 21 2007, 01:29 PM) [snapback]542603[/snapback]</div> Interesting stuff. In my way distant past, before digital, I was involved with some experiments on sound localization. Back then audio delays were accomplished mechanically using tape loops, or garden hose in a box with a speaker at one end and mic at the other. One of things discovered was that humans localize on the first sound arriving at their ears. The experiment set up two speakers in a room, one on the left, one on the right. The same audio was sent to both except one speaker amp processed it through a delay device, the "Cooper Time Cube". This added something less than 30ms of delay. The result was even though both speakers were set to equal volume, the listener localized on the non-delayed speaker and would swear the other speaker was off. A practical application of this was the ability to reinforce the overall sound level in the room with the appearance of all the sound coming from just one point. Now with the advent of inexpensive digital delay devices even more can be done psycho-acoustically to make your Prius sound like a concert hall.
Except the Prius doesn't have this feature . This is found on the Camry and is the first vehicle to feature JBL's DSS or Distributed Subwoofer System. This eliminates the need for a dedicated woofer and allows the bass to be distributed evenly among the speakers but producing bass quality equal to that of a dedicated woofer. Oh and thanks for the history lesson. That's actually quite neat. I'd like to try that speaker experiment for myself and see (rather hear) what it sounds like.
<div class='quotetop'>QUOTE(Tideland Prius @ Nov 21 2007, 05:05 PM) [snapback]542719[/snapback]</div> I understand. I was thinking that the effect could be added with an after-market device to the Prius or other cars. The sound localization experiment showed that if the delay was less than 30ms, it worked as described. At 30ms or more the brain no longer fused the sounds to a single point but could start to perceive a echo.
<div class='quotetop'>QUOTE(banjoman @ Nov 21 2007, 06:13 PM) [snapback]542743[/snapback]</div> I wouldn't know how lol. This is waaay out of my league.
Or, "Psychoacoustics" could also mean, "Turn that up any louder and I'm gonna kill you!" Cue Norman Bates sound effect.
