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Technical Bulletin
Reducing echo
Revision 1.3, August 2005
Under some conditions users may experience echo while using SecureGSM™, which are related to the incorrect level settings of microphone sensitivity and speaker volume during a SecureGSM™ call.
Recently, we have identified that the system settings on devices vary considerably, and therefore no standard operating levels are present across different devices, be they from the same manufacturer or otherwise.
Essentially what this means is that users of a particular device may have perfect communication with SecureGSM™ default settings, while others, using a different model or revision may experience unacceptable echo and spurious artefacts if their application settings are not adjusted correctly.
It is important to understand that any echo you hear will be primarily the result of the settings of your called/calling party’s device. Therefore, it is important that all users of SecureGSM™ optimise settings for their device in particular.
When the microphone sensitivity and/or the speaker volume are at excessively high levels (and/or combination of the two) the SecureGSM™ application may experience difficulties providing effective echo suppression due to being outside its operating range.
Below are some recommendations for particular devices which we have found to need such adjustments. If your device is not on the list, or you still find unacceptable echo, please follow the General instructions on how to optimise settings for your device below.
As of the August release of SecureGSM™ Evaluation, the following default settings will be assigned on a per-device basis upon installation:
HTC Himalaya:
I-mate Pocket PC, O2 XDA II, Qtek 2020, MDA I, Dopod 696, etc.
In call microphone sensitivity: +10
In call speaker volume: +4
HTC Alpine, HTC Blue Angel, HTC Magician:
I-mate PDA2K, I-mate JAM, O2 XDA IIs, O2 XDA IIi, MDA III, O2 XDA II MINI, MDA COMPACT, QTEK S100, etc.
In call microphone sensitivity: 0
In call speaker volume: +4
Note: These settings are only used during a SecureGSM™ call and are restored to default system levels when SecureGSM™ is in idle (Ready…) or off.
The default installation settings apply if you have not modified them manually or if the “Restore Default” button is applied.
Please note: If the “Use System Setting” option is enabled, then the echo suppression mechanism will be deactivated and may lead to unacceptable levels of echo.
We suggest keeping the “In call microphone sensitivity” setting un-modified unless you have an important reason to do so.
We have found that the default settings which are applied upon installation to be optimal for the majority of users. Please do not increase microphone sensitivity settings above the recommended default level, as this may cause drastically increased echo for your called/calling party. Generally speaking, it is much better for the other party to increase the “In call speaker volume” setting, rather than increasing the microphone sensitivity on your device.
The “In call microphone sensitivity” and “In call speaker volume” settings can be adjusted in real time during a SecureGSM™ call if you find that an adjustment is needed.
Advanced Audio Control
As of the August release of SecureGSM™ Evaluation, the Advanced Audio Control functionality will be included with in the application. Advanced Audio Control can be accessed in two distinct ways.
1. Tap on the “Advanced Audio Control” icon in the taskbar.
2. Press-and-hold the grey “backspace” key in the SecureGSM™ Dial screen.
All changes you make using Advanced Audio Control are live and effective immediately and correspond to values in the “Microphone” and “Volume” tabs in SecureGSM™ Settings.
Essentially the Advanced Audio Control screen provides easy access to the Audio settings for SecureGSM™ in one convenient screen.
Use the up/down buttons for the “In call microphone sensitivity” (mic) and “In call speaker volume” (vol) to make adjustments as per the following recommendations.
At the bottom left of your screen, a readout for the current settings are shown.
Device Volume control slider
The Volume control slider on your device is always active during a SecureGSM™ call. Use this volume control at any time during a call to temporarily increase or decrease the speaker volume.
Unlike the Advanced Audio Control, this works as a temporary volume setting and is not memorised for future SecureGSM™ communications.
Essentially, the Advanced Audio Control “In call speaker volume” sets an optimal starting point for all SecureGSM™ communications, and any temporary volume adjustments you need to do during a call can be made using the device Volume control.
Note: If you find that you need to adjust the speaker volume for the majority of your SecureGSM™ calls, then you should adjust the “In call speaker volume” setting either using the Advance Audio Control screen, or by using the SecureGSM™ Settings so as to memorise your optimal “In call speaker volume” for all SecureGSM™ calls as per the General instructions on how to optimise settings for your device.
The Advanced Audio Control “In call speaker volume” is capable of making much finer adjustments to your “in call” speaker volume and should be used to set your optimum operating level.
General instructions on how to optimise settings for your device.
(Usually required upon first use only)
If you are experiencing excessive levels of echo, then the device of the other party (your called/calling party) requires adjustment.
You should ask the other party to:
1. Open the Advanced Audio Control screen and decrease the “In call microphone sensitivity” (mic) by five (5) increments.
If this does not solve the issue,
2. Adjust their “In call speaker volume” (vol) to the minimum level of comfort.
This should eliminate any problems with echo. If you are still experiencing echo then,
3. Ask the other party to further decrease the “In call microphone sensitivity” a further three (3) to five (5) increments.
4. Ask the other party if they are experiencing echo, if they are, then you should repeat steps 1 -3 above on your device. That is, you should now open the Advanced Audio Control on your device and decrease the “In call microphone sensitivity” (mic) and then adjust “In call speaker volume” (vol) to a comfortable minimum level.
Once these procedures have been followed, press “ok” to close the Advanced Audio Control screen.
Note: The changes which you make in the Advanced Audio Control are memorised for all future “in call” communications. It is recommended to keep these settings from that point on. If you find you need to further fine tune the settings, please follow the above instructions, and adjust the settings in smaller increments.
In the majority of cases decreasing “In call microphone sensitivity” 5-10 units down will improve and likely completely eliminate any echo effects. Please remember that keeping your microphone sensitivity level down at any time is good idea to make conversations pleasurable for both yourself and other parties while in a SecureGSM™ call.
Also, please note that Advanced Audio Control is enabled for the majority of HTC manufactured devices and some others. Some non-HTC manufactured devices may be found incompatible with SecureGSM™ Advanced Audio Control and therefore microphone sensitivity controls will be automatically disabled. SecureGSM will be looking at providing broader compatibility for devices currently unsupported by Advanced Audio Control in upcoming versions of SecureGSM™ software.
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