Dave's ESL Cafe's Student Discussion Forums

[Joseph@Shiga]

Hi everyone,

In the field of electric communication, there is a word "multipath" that causes (or cause) noise in a received sound or an image.

Please tell me whether this word "multipath" is countable or uncountable noun.

Thanks alot in advance.

Joseph@Shiga

[lotus]

Hi Joseph,

Multipath is generally used as an adjective - multipath distortion, noise, attenuation, drop-out, etc.

When used as a noun, it is a collective noun and is singular. Multipath means multiple paths, collectively.

Multipath is an electrical transmission phenomena of radio waves (actually any electro-magnetic wave). It's just that we notice it more on radio and wireless communications (hearing frequencies). Upon transmisson, a radio wave will deflect or bounce off various objects and split up and arrive at a specific point at different times. This causes distortion, noise, attenuation, drop-outs, etc. We can compensate for that somewhat electronically, but not totally.

To experience this phenomena indirectly, switch the wires on one of your duo speakers. You will notice that voice and music no longer sound natural - especially at low frequencies. The lower frequencies will be attenuated because of the phase shift between speakers. In fact, at one specific frequency, it will cancel out altogether and you will hear nothing. At medium frequencies, sound will seem to "move around" and may feel a little "echoey." Music will have a false and unnatural three-dimension feel to it, with loss of directional clarity. Experienced technicians will be able to detect out of phase speakers without checking the wires. This phase-shift phenomena of multipath transmission is a major cause of drop-out in wireless electronic communications.

This site has a good overall discussion on multipath transmission.
http://www.audio-technica.com/cms/site/ba13005b4e8c353f/index.html

This site has a more technical discussion on multipath effects.
http://www.cdc.gov/NIOSH/fire/pdfs/FFRCSch4.pdf

Although phase-shifts can have a detrimental effect, it can also be used positively to manipulate or simulate certain sound qualities, such as spatial or holographic effects.

Two interesting sites on "holophonic" sound.
http://www.sound-ideas.com/holophonic.html
http://itotd.com/articles/335/holophonic-sound/


--lotus
_________________
War does not make one great --Yoda

[Joseph@Shiga]

Hi Lotus-san

Many thanks for your detailed explanation.
I goccha.

Joseph