Message-ID: <436F5602.1040105@web.de>
From: Dirk Stockmann <dirk.stockmann@web.de>
MIME-Version: 1.0
To: bluez-users@lists.sourceforge.net
Subject: Re: [Bluez-users] Periodic noise on microphone with bt_sco (BTA-6030
 Dongle, Motorola H500 Headset)
References: <436F1C3B.5020002@web.de> <436F4D85.4030404@csr.com>
In-Reply-To: <436F4D85.4030404@csr.com>
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Sender: bluez-users-admin@lists.sourceforge.net
Errors-To: bluez-users-admin@lists.sourceforge.net
Reply-To: bluez-users@lists.sourceforge.net
Date: Mon, 07 Nov 2005 14:26:26 +0100

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Hi,

Steven Singer wrote:
> At what rate are SCO packets transmitted in an HV3 link?

thanks for your reply, this is already a good hint.

> Based on the frequency, this looks (sounds?) like an electrical
> problem. Many parts of the RF will have duty cycles of 266 Hz. Even
> the current demand of the module will have a profile with this
> frequency (it may pulse from a few milliamps up to 50 milliamps at
> this rate, with sharp edges).
> 
> I expect you're getting pickup from the electronics on the module onto
> the microphone cables,or, more likely, the audio card in the PC -
> they're notoriously badly shielded, you can even hear when you drag a
> window round the screen.

But when the headset is connected to my Mobile Phone there is no noise,
so it is unlikely that it is related to the headset itself. And I always
thought (maybe wrong?) that the processing inside of the PC is pure
digital. So there should be no noise on a recorded file. Besides from
that my PC has a very good audio system with no noise at all.

I think that there is a problem with the processing of the received
packets that creates the spikes in the signal.

Regards,
Dirk

- --
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