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Silence Supression

DanCarroll
Frequent Advisor

Silence Supression

I am using PCxset on computers located in India. The NBX is in Connecticut.



Once the network was set to use priority, EF class. then I noticed static and whoosing sounds in the silence between words.



I removed silense suppression and these noise went away.



Is silence suppression  recognized accross a WAN?



Cisco routers are in use



7 REPLIES
merlin_1
Super Advisor

Re: Silence Supression

Silence suppression should be off on all devices . Not sure why you would use it to begin with .



DanCarroll
Frequent Advisor

Re: Silence Supression

I have had silence suppression on since I started using VTL's.



The book says it reduces packets by 40%.



Why wouldn't I use it? or When should it be used?



merlin_1
Super Advisor

Re: Silence Supression

Silence suppression has been used in the past to reduce a white noise that can show up on the voice . In over 9 years , I have not used it as it can cause issues . I am not sure what you would use it for , eg , reduce packets , but I can see it removing some of the packets . Compression can be used to reduce overhead on the packets . You can prob troubleshoot your network and find the root cause of why the change sin your settings caused the issue but again , I do not know of anyone that uses Silent Supression anymore !



Page 501 of the manual states for a condition known as congestion , silence suppression would be used to remove some packets .



 





You can reduce NBX system’s bandwidth



requirements by enabling 



“silence suppression,” but doing so



compromises audio quality. NBX



Telephones generate voice frames at



regular intervals for the duration of



a connection. These frames normally



continue when no one is speaking.



When silence suppression is enabled, the



NBX system sends a “silence



indicator” when the NBX Telephone



senses the start of a silent period.



When another NBX device receives this



indicator, it inserts “white noise”



until it receives the next frame that



contains real voice. All subsequent



“voiceless” frames are suppressed



during the silent period. However,



most telephone users will notice the



difference between genuine silence



and generated silence.



 





 



 



 



 



 



 



 



This type of silence suppression applies to Layer 2 Ethernet transfers. At



Layer 3, the ConneXtions software achieves a similar result by not



sending empty packets during a silent period. The receiving ConneXtions



gateway generates a silence indicator or sends frames filled with silence,



depending on the silence suppression mode.



 



Congestion





Users notice congestion when audio “breaks up” during a call.



Congestion can occur anywhere on the



network, for example, at an



overloaded LAN (local or remote), at an



overloaded router or firewall, or



within an overloaded internet. Because



voice packets are only significant



during a conversation, IP networks



respond to congestion by discarding



data packets they cannot accommodate.



Resending or delaying packets is



not an effective solution.



At the local level, congestion symptoms can be subtle. For example,



routers from different vendors can



respond differently to congestion



because of the way they prioritize their



response to packet congestion.



When considering communications



problems, it is important to maintain



reserve capacity and to use a systematic



approach that considers the



entire, end-to-end, connection.



This message was edited by merlin on 2-9-10 @ 8:03 AM
DanCarroll
Frequent Advisor

Re: Silence Supression

ok.



Silence suppression is off on all my units, including VTL's connections also.  Right?



merlin_1
Super Advisor

Re: Silence Supression

yes , I would



Then retest everything and I'm sure you will be happy with the results !



 



DanCarroll
Frequent Advisor

Re: Silence Supression

thank you!!



merlin_1
Super Advisor

Re: Silence Supression

My Pleasure !



Email / call / IM if needed !