Compatibility of 2.3 GHz 4G mobile with assistive listening devices

To investigate the impact of 2.3 GHz 4G mobile phones on ALDs, we focused on evaluating any influence on the audio quality of the speech file transmitted over the radio link of the ALD systems. During the testing, over 200 audio files were recorded and assessed.

The following ten example files are published as a complement to test results and analysis presented in the report.

File group A

File group A contains five audio samples referred to as outliers in sections 4 and section 5, representative of some variations in the audio quality potentially due to one of several reasons including 4G interference. To highlight the effect of interference, each sample file was edited by concatenating 10 seconds of the baseline file (recorded without the 4G signal) with 10 seconds of the test file (recorded with the 4G signal signal).

• Outlier No.1 [concatenated baseline and video call test file] – “GA_1” (WAV, 1.5 MB)
• Outlier No.2 [concatenated baseline and voice call test file] – “GA_2” (WAV, 1.5 MB)
• Outlier No.3 [concatenated baseline and voice call test file] – “GA_3” (WAV, 779.6 KB)
• Outlier No.4 [concatenated baseline and voice call test file] – “GA_4” (WAV, 1.5 MB)
• Outlier No.5 [concatenated voice call test file in the UK auction band and voice call test file in the UK guard band] – “GA_5” (WAV, 1.8 MB)

File group B

These samples are examples of a wide range of audio qualities observed in our test programme. Each sample files lasts for 10 seconds.

• Best quality sample [MOS 4.6] – “GB_1” (WAV, 640.0 KB)
• Good quality sample [MOS 3.2] – “GB_2” (WAV, 640.0 KB)
• Medium quality sample [MOS 2.5] – “GB_3” (WAV, 640.0 KB)
• Poor quality sample [MOS 1.6] – “GB_4” (WAV, 640.0 KB)

File group C

File group C has only one sample file, denoting the largest degree of variation in the audio quality between the left and the right ear for a baseline file, for which POLQA gave a delta MOS of 0.94. The audio samples last for 10 seconds as well.

• Large discrepancy in quality between two ears [delta MOS 0.94] – “GC_1” (WAV, 1.5 MB)