FIELD APPLICATION NOTE Audio Quality Tuning for IP Telephones Issue 2.0 July 10, 2007 COMPAS ID – 120942 Abstract IP Telephones can be fine-tuned to provide optimal audio quality performance by administering audio parameters in the file server settings file. This document provides a guide to administering those parameters as well as a description of each parameter and its range of settings.
1 Introduction This document describes the audio tuning parameters administrable via the 46xx/96xx settings 1 file and adjustments that can be made to optimize the phone for specific customer environments and audio impairments. The available range of programmable system parameters will allow the engineer/technician to adjust the audio performance of the IP Telephone (IPT) for the various customer locations and their respective environments. After being introduced in R2.
The ability to turn off the expander (now more appropriately called NR ) was added in R2.7 and a more aggressive noise reduction setting (Excessive noise) was added in R2.810. The reason for the name change from expander to noise reduction (NR) is to more accurately describe the actual 4 function being used – noise reduction (NR) as opposed to expansion (Exp). See Table 2 and 3 in Appendix A. Because of the two added states in AUDIOENV, the AUDIOENV matrix has grown from 108 to 299 possible settings.
AGC_Dyn_Range - Receive AGC Dynamic Range: Used to boost low-level speech from the far end party. Be aware that increasing the AGC dynamic range will not only boost speech, but will also boost any low-level environmental noise from the far end or circuit noise from network equipment in the call topology. • AGC dynamic range has default value of 0 (+/-9dB). Other available settings are 1 (+/12dB), 2(+/-15dB), and 3 (+/-18dB). NR_Thresh_HD - Headset Noise Reduction Threshold.
R2.4 or later (which has a default AGC dynamic range of +/- 9dB), they should disable AGC on the headset, handset, and/or speakerphone depending on which mode of communication they are using to listen to the call. Disabling AGC will prevent the phone from boosting low level receive signals (such as noise). 4.2 Noisy Offices A noisy office is defined as having a dBA reading of about 60dBA.
AUDIOENV Variable Settings for Noisy Office If Headset user Customer’s current AGC setting If Handset user 1 choice +/- 15dB 63 57 59 +/- 18dB 90 84 86 st nd 2 choice (*) (*) Note that these settings add loss to the transmitted speech and can affect the ability of the far-end party to hear the headset user AUDIOENV Variable Settings for Very Noisy Office If Headset user Customer’s current AGC setting If Handset user 1 choice +/- 9dB 18 6 8 +/- 12dB 45 33 35 +/- 15dB 72 60 62
AUDIOENV Variable Settings for Excessive Noise If Headset user Customer’s current AGC setting If Handset user 1 choice +/- 18dB 249 297 st nd 2 choice (*) 299 (*) Note that these settings add loss to the transmitted speech and can affect the ability of the far-end party to hear the headset user 4.2.
4.3.2 Agent to Agent Calls across Networks – with background noise issue Under some circumstances, calls between agents across the customer’s network may have a different complaint. The complaint may be that the agent has trouble hearing the other agent even after increasing their receive volume to maximum. In this case, an AUDIOENV value of 35 will help boost this level by setting the AGC dynamic range of +/-12dB.
MedPro, an IP phone user will maintain the same talker level experience they have with an IP phone user as with a DCP phone user. The Terminal Parameter settings on page 2 that do affect the IP Telephones are the following: The Volume for IP Types setting can be set to either retain the receive volume between calls or leave the levels at default between calls. 5.5 Loss Plan The loss plan in CM provides for the ability to change transmit and receive levels for any loss group (such as IP Telephones).
INDEX 1 INTRODUCTION ................................................................................................................................................ 2 2 DOCUMENT HISTORY ...................................................................................................................................... 2 3 AUDIO QUALITY TUNING PARAMETERS .......................................................................................................... 2 3.1 TUNING PARAMETER CHANGES FROM R2.
APPENDIX A: AUDIO PARAMETERS COMPAS ID 120942 © 2003-2004 Avaya Inc. All rights reserved.
SIDETONE SETTINGS As indicated in the main text of this document, both the AUDIOSTHD and AUDIOSTHS variables provide sidetone customization (for both headset and handset, respectively). One step will provide approximately 3dB of change (think of it as one chevron of volume control). A step below reduces the loudness of sidetone – a step above increases the loudness of sidetone. Table 1 provides sidetone level settings for all of the IPT releases that provide audio quality tuning parameters. Release R2.
For example, an AUDIOENV setting of 0 (zero) is the default setting for all audio parameters. If an AGC of +/- 12dB is required (with default settings for the other variables), an AUDIOENV setting of 27 would be used. If the customer problem at that point involved ambient noise being transmitted to the far-end by a handset, the AUDIOENV setting would then change to 36 (this value only changes the handset noise reduction setting while keeping the AGC setting of +/- 12dB).
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APPENDIX B: QUICK START AUDIO PARAMETER SETTINGS COMPAS ID 120942 © 2003-2004 Avaya Inc. All rights reserved.
THE QUICK START TABLE The table below provides settings that have successfully been used at customer sites to correct audio quality complaints. Note that these settings are applicable only to a customer with a current AUDIOENV setting of zero (default). See Appendix A for customers who have a setting other than zero (default) in order to use the matrix to locate the correct AUDIOENV setting. Match the symptom in the table with the customer environment/complaint and make the First adjustment provided.
APPENDIX C: SOUND LEVEL MEASUREMENTS COMPAS ID 120942 © 2003-2004 Avaya Inc. All rights reserved.
SOUND/NOISE: Our ability to hear sound is different at different frequencies. Because of this, we do not perceive sound equally for the same level at one frequency as we do for another frequency and so sound/noise at the lower and higher frequencies is not as annoying as those at the middle frequencies. In order to measure room noise so that all the frequencies are equal, a sound level meter with the ability to correct for all frequencies is needed. Such a correction when performed is known as A-weighting.
• Speakerphone - complaints (local noise affecting speakerphone operation). If unfamiliar with any 16 part of the test setup, read the User Guide provided with the SLM. o o Setup: 1. Set the Weighting to “A” and the “RESPONSE” to “Fast”. 2. Set meter range so that the signal level bars are close to the “0” at the bottom of the display. Test: 1.
