[MV] Re: Results of microphone tests

[David Morrison]

>  >The Andrea 600 could not be made to work with iListen at all, and was
>>marginal with Via Voice. Its accuracy was no better than the 7100,
>>and in some tests much worse. Other people report that this mic
>>provides better accuracy than the 7100 (with Via Voice? Has anyone
>>got it to work with iListen?). In audio tests, its signal was around
>>25-50% of that of the 7100, which is apparently to be expected
>>because of the nature of the noise cancelling mechanism.
>
>I don't have any problems using my Andrea 650 microphone with iListen.
>All I need to do is unplug my PowerBook from AC power to get rid of the
>hum, and it works fine. The Andrea 650 is the same microphone as the
>Andrea 600, but with stereo headphones.

Were you by chance using OS 9 and an analogue connection (rather than 
a USB adapter)?

I did not mention how I did the audio tests. I found a program 
(Player Pro) that displays the sound input as an oscilloscope 
display. This allowed me to measure the amplitude of the input waves, 
ie, the peak volume of the signal. I also noted the signal level 
shown on the VU meter in the Sound system preference panel.

In all cases, I repeated the same phrase about a dozen times, 
speaking in a normal voice. I did this on several days just to 
compensate for my voice changing or the effects of system reboots, 
etc. Gain in all cases was set to the maximum.

Out of curiosity, I tried the same tests under Mac OS 9.2.2. For both 
USB connections (7100 and 600/Pod), the results showed a slightly 
weaker signal than OS X. However, the analogue connection showed 
significantly better signal strength than under OS X. In fact, the 
600/NE Mic combination on OS 9 was actually even stronger than the 
7100 on OS X.

The results were:

Mic		VU Meter (OSX)	Player Pro (OSX)	VU Meter 
(OS9)	Player Pro (OS9)

Andrea 7100	15/15		4 cm		16/16		4 cm

Andrea 600/Pod	8/15		1 cm		5/16		1 cm

Andrea 600/NE Mic	7/15		0.75 cm		16/16		4 cm+

I'm not sure what to conclude from this. It looks like the gain is 
similar for USB devices under both operating systems. However, the 
gain for analogue devices under OS 9 seems to be much, much higher.

As such, using OS9 with an analogue mic may well produce the best signal.

Regards

David
-- 
David Morrison, Systems Specialist
Flexible Learning Administrator and Blackboard Project Manager
Communication and Information Services, University Services
The University of Newcastle, Australia
E-mail David.Morrison at newcastle.edu.au
Ph +61 2 49215397   Fax +61 2 49217087