Background hissing noise on CP-7920

[geand]

Hi all,

I have CP-7920 Wireless IP-Phones connected to an Access-Point 1200. The Problem is during a call the called party hears a continous background hissing noise. I found nothing how to turn this off. The wireless connection in principle is regarding to signal quality ok. The 7920 is running the latest Firmware 7920-sccp.1-0-6 and the AP 1200 is running the latest IOS 122-13.JA1. I´ve as well configured QoS on the WLAN.

What could be the solution for this problem?

Thanks in advance,

Gerald

[sbilgi]

Try tuning the output attenuation.

[geand]

I´ve tried tuning the output attenuation of the Wireless Phone but it does not really help.

But anyway, thanks

[gdelion]

I'm getting the same problem with my customer but with AP 1100.

Did you get more news since your post ?

[geand]

unfortunately I got not more news since my post.

I found out that it is not related to the AP because I´ve also experienced the same problems with a NetGear AP.

[geand]

The problem is related to an issue in the Firmware of the 7920 in conjunction with G711 a-law.

CSCed01562:

Static noise can be heard on the Cisco Wireless IP Phone 7920 when the phone is using a-law companding.

Workaround: Use u-law companding, if possible. If that is not possible, there is no workaround

After changing the codec to G711 µ-law the problems has been solved.

[gdelion]

I have done a simple test to verify if this issue was due to this bug. But simply when you call an other IP Phone (7960) from the 7920 IP Phone, there is a background noise heared on the 2 IP Phones (7960 & 7920) during the conversation.

The codecs tested were G729 and G711 ulaw.

[geand]

It seem that you have a different issue.

My problem was a static background noise not on the 7920 but on the other end. Whereas there was no difference whether it was a call within the IPT environment or to the PSTN.