keithe@tekgvs.UUCP (10/21/86)
In article <1371@uwmcsd1.UUCP> shop@uwmcsd1.UUCP (Thomas Krueger) writes: > >Absolute phase in this case refers to the idea that most music is "positive >pulses" and not "negative pulses". Take for example a drumstick hitting a >cymbal. The first wave that hits your ear will be a compression followed by >a rarefaction, etc. Many people think that if the first reproduced wave >that hits your ear is a "negative" rarefaction, that the music will sound >unnatural. Empirically, I tend to agree. Others say that most music is >mostly "positive" pulses with much fewer "negative" pulses. Are you telling me that my eardrum wants to go "in" before it goes "out?" To borrow a punchline form an old joke*: "How do it know?!" I'm having a LOT of trouble believing this one... keith *Joke will be supplied upon request :-)
ben@catnip.UUCP (Bennett Broder) (10/23/86)
In article <1842@tekgvs.UUCP> keithe@tekgvs.UUCP (Keith Ericson) writes: >In article <1371@uwmcsd1.UUCP> shop@uwmcsd1.UUCP (Thomas Krueger) writes: >>Absolute phase in this case refers to the idea that most music is "positive >>pulses" and not "negative pulses". Take for example a drumstick hitting a >>cymbal. The first wave that hits your ear will be a compression followed by >>a rarefaction, etc. Many people think that if the first reproduced wave >>that hits your ear is a "negative" rarefaction, that the music will sound >>unnatural. Empirically, I tend to agree. Others say that most music is >>mostly "positive" pulses with much fewer "negative" pulses. > >Are you telling me that my eardrum wants to go "in" before it goes "out?" > >To borrow a punchline form an old joke*: "How do it know?!" > >I'm having a LOT of trouble believing this one... Another way to think of it is: when the diaphram in the microphone moves in, so do the drivers in your speaker. Some instruments (like the trumpet) have very asymetrical wave forms, so this could make an audible difference. -- Ben Broder {ihnp4,decvax} !hjuxa!catnip!ben {houxm,topaz}/
sasaki@endor.UUCP (10/23/86)
A friend of mine did some psycho-acoustic tests and it was easy to tell the difference with hand claps and human voice, and almost impossible with musical instruments that included strings, reeds, and horns. The tests weren't exactly double blind, my friend made a tape where pairs of test sounds were recorded with about 5 seconds of silence between. The order of the sounds was determined by a dice throw and my friend tried hard to make everything else equal. Everyone listened to the same tape, alone in the testing room. We were told to mark on a sheet of paper whether the sounds were the same or were different. I'm sure that there were some biases introduced, but the test was pretty good. As for whether the results of the experiment have any bearing on music heard on audio system, I can't say, and don't want to get flamed for an opinion either way. I just present this information as an indication that you can tell the difference in absolute phase under (highly artificial) test conditions. ---------------- Marty Sasaki uucp: harvard!sasaki Strategic Information arpa: sasaki@harvard.harvard.edu 80 Blanchard Road bitnet: sasaki@harvunxh Burlington, MA 01803 phone: 617-273-5500
pmr@drutx.UUCP (RastocnyP) (10/25/86)
[?] The psychoacoustic phenomenon I observe on my system when absolute phase is manipulated (and it is in many albums, J.M. Jarre's "Oxygene" comes immediately to mind, where absolute phase trickery is used) is that the soundstage leaps from behind the plane of the loudspeakers to in front of the plane of the loudspeakers. So an album recorded out of absolute phase (Sheffield Lab even produced one) has the psychoacoustic illusion that the musicians are standing in the middle of the listening room. But in "Oxygene", Jarre uses this technique creatively to start sounds, say in the left channel in front of the loudspeakers (out of phase) and the pan the sound to the right channel, invert the phase (in phase), reduce the volume, and increase the echo content. The result is a psychoacoustic illusion that resembles a small model rocket launched from the left of and in front of the left loudspeaker and traveling to a point way to the right of and behind the right loudspeaker. (The other sounds in this all electronic music album are contained behind the plane of the loudspeakers.) Pink Floyd, Dire Straits, the Cars, Kitaro, and Vangelis have also used similar absolute phase trickery in their albums. While absolute phase on most stereos is not blatently obvious (the system must have a significant amount of soundstage depth), some albums on some refined systems can produce very interresting effects. Yours for higher fidelity, Phil Rastocny AT&T-ISL ..!drutx!pmr