About spectrum of speech and fax transmission
in [DSP]
|
From: VSP on 30 Jan 2006 10:30 hi all, Someone please tell me why the spectrum of speech rolls off towards the higher frequencies ?????? I am a newbie to DSP so, simple terms please as far as possible. I am hoping to use this fact to distinguish it from other data transmissions such as fax. (this was suggested to me by Mr.Vladimir Vassilevsky on Comp.DSP only) Yes Mr. John I am thankful to u also for ur reply. I am trying to read about ITU-T T.30 protocol but could not find a good enough source online. Mr.John had suggested using the two tone (frequency) handshake between two fax machines as a way of identifying fax transmissions. All ideas are welcome and appreciated.
From: Alex on 30 Jan 2006 10:44 Hi, if you are looking for info how fax technology is different from voice modem communication the answer is simple: they used different signals what controlled by correspondent international standards. Read the standards and you will know everything about voice and fax transmission. You don't need to invent a wheel in the topic. Good luck, Alex
From: VSP on 30 Jan 2006 11:00 >Hi, >if you are looking for info how fax technology is different from voice >modem communication the answer is simple: they used different signals >what controlled by correspondent international standards. Read the >standards and you will know everything about voice and fax >transmission. You don't need to invent a wheel in the topic. >Good luck, >Alex > > Hi, Please tell me if there is some online resource where I can find these international standards, because I couldnot find the actual ITU-T T.30 fax transmission protocol at all - only annoying referals to it being conformed to. Thx in advance.
From: Alex on 30 Jan 2006 22:39 Hi, T.30 is very old protocol and, you are right, I was not able to google one, too. The only way to get the text happened with me when I used to work as a modem developer at Cirrus Logic. To get voice protocols is easy job. Look on ETSI site. They have everything, including homologation, at least 5 years back, when I maintained Intel modems I downloaded about 600 pages of ETSI standards covering all modem protocols except fax. :( Good luck, Alex
From: Vladimir Vassilevsky on 31 Jan 2006 01:19
VSP wrote: > hi all, > Someone please tell me why the spectrum of speech rolls off > towards the higher frequencies ?????? I am a newbie to DSP so, > simple terms please as far as possible. This is the scientific fact. Throat is made of soft materials. > > I am hoping to use this fact to distinguish it from other > data transmissions such as fax. Sure. This simple method works very well. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com |