The NAC's real-world testing scenarios focus on these six key technical categories.



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Real-world audio testing is performed on the live carrier network to ensure the test results reflect the actual customer experience. Our goal is to identify customer-affecting issues that negatively impact the consumer experience. Audio recordings are captured on a mini-CD and included with each report.

Testing attempts to determine performance of three main audio characteristics:

  1. Echo heard on the landline side of the call while the device is operated at the maximum volume level
  2. Audio levels in comparison to a benchmark device
  3. The effect of background noise on both the uplink and downlink audio

Some audio technology tested by the NAC includes:

Uplink Audio

This is the audio that the far-end listener hears - usually the land-line side of a conversation.


All modern digital cellular phones use voice coders to code the human voice. This causes a delay in speech transmission that can be perceived as an echo to the far-end caller.

Downlink Audio

This is the audio that the phone or accessory user hears.

Wind Noise

Phones and headsets do little good if the far-end party cannot hear the user when operating in a windy environment. The NAC tests the headset's or mobile phone's ability to minimize the effects of wind.

Duplex Performance

This is the ability to hear and understand the other party when both parties are speaking at the same time.


GSM phones and Bluetooth headsets may sometimes introduce a 'buzz' sound into the uplink or downlink audio path. This can vary depending on the channel, frequency band, and power level at which the mobile phone or headset is operating.

Background Noise Performance

Both the uplink and downlink audio are tested and evaluated in varying degrees of background noise.

Volume Control

An accessory can often control the volume of the downlink audio. This interaction with the phone is tested to ensure customers are not negatively impacted.

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