Huawei Mate 9 Review: Call Quality
Author:Soomal
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Few manufacturers had paid attention to its call quality, except Huawei Mate 9. Huawei introduced the network support, directional audio capture and 4 microphones for clear conversation on its website for Mate 9. How will those functions perform for users?

As the Mate 9 adopts Huawei HiSilicon processor, the wireless and audio solutions have to be developed by Huawei themselves. By now, most Android smartphones belong to dual-mic noise reduction solution, the main microphone picks up sound waves, the assisted microphone on the top or near the rear camera to eliminate noise. Although two microphones are able to reduce most noise, the more microphones the more sampling for noise reduction. For example, iPhone 7 and 7 Plus have 4 microphones, two of them are located on the bottom, on either side of the Lightning port, one near the old headphone jack, and one is located on the back, between the True Tone flash and iSight camera. [ Because there are only a few Mate 9 teardown, we cannot figure out where are those microphones on Mate 9, and use iPhone 7 as an example.] Except calling, these four microphones are always listening for voice assistant, and helps recording. However, restricted by cost, few smartphones under 2000 RMB (about $300) adopt 4 mics.

Huawei Mate 9 features a dual-end noise reduction on its Chinese website. So, what is dual-end noise reduction? A regular noise reduction process is using a DSP to identify background noise features that is different from speech, then subtracting this "bad" sound from the rest of the transmitted signal, while when receiving the speech signal, the DSP will also identify and reduce the noise. Dual end noise reduction means identifying and subtracting noise on signal input from both ends. However, it is not something new, Moto Razr, Droid that released years ago, or recent Qualcomm processor equipped smartphones had equipped with this kind of noise reduction.

Earpiece Speaker Test

The Huawei Mate 9 provides whole world of connections with its patented integrated Nano SIM + Micro SD slot and secondary card supporting WCDMA and GSM.

We place this cell phone indoor with normal signal, and set the call voice volume to maximum, then call 10010 [GSM], which is China Unicom customer service hotline, and 10086 [VoLTE], which is China Mobile customer service hotline. Then use professional sound card and microphone for recording and analysis.

Testing Item Mate 9 @ VoLTE Mate 9 @ GSM Xplay 6 OPPO R9s iPhone 7 Plus Huawei P9
Output Level of Earpiece,dB -10.54 -8.48 -10.56 -11.5 -8.06 -7.59

Although the earpiece output volume is lower than that of P9, the earpiece performance of Mate 9 is satisfied for its fuller sound.

Loud Speaker Test

Speaker test was undertaken indoors with ambient noise level at 40dB or less, we turn up the ringtone volume to its maximum, and then use a sound level meter to measure sound level at the distance of one meter from the phone.

Testing Item OPPO R9s MOTO Z iPhone 7 ZTE AXON 7 One Plus 3 Xplay 5S Huawei P9
Face Up,dB 78.7 74.1 74.1 76.9 76.8 78.7 74.8
Face Down,dB 77.0 75.2 78.6 77.5 77.3 80.4 74.7
In Camera Bag,dB 69.4 69.8 72.6 72.3 72.3 73.4 67.4

The Mate 9's loud speaker has a higher maximum volume compared with P9, but sounds thinner and harder.

Noise Reduction Test

We place this phone indoors with ambient noise level at 32db or less, in the middle of the room, we use a human-like structure "handholding" the phone to send voice signal, and put surround speakers in a certain distance playing 5 kinds of simulating ambient noise at 6db SNR. Then we standardize the recording from this end, and run a specific program comparing this recording with raw speech recording and noise-speech mixed recording to get noise reduction level, SNR improvement and SNRI-to-NPLR difference quantitative result.

Testing Item[GSM Hand Holding] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 47.0 42.3 48.4 47.8 39.9
SNR Improvement,dB[Higher is Better] 35.9 29.2 38.1 36.6 27.7
SNRI-to-NPLR difference,dB[-4 to 3] -3.4 0.2 -5.3 -4.3 0.9
Testing Item[VoLTE Hand Holding] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 43.3 40.4 47.0 45.7 38.6
SNR Improvement,dB[Higher is Better] 33.2 27.6 37.2 35.1 29.3
SNRI-to-NPLR difference,dB[-4 to 3] -2.9 -0.5 -5.7 -4.7 0.2
Testing Item[Hand-Free Mode] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 24.4 24.0 34.1 36.2 19.3
SNR Improvement,dB[Higher is Better] 15.8 17.0 27.0 25.3 15.6
SNRI-to-NPLR difference,dB[-4 to 3] -2.3 -0.9 -6.6 -5.1 1.6
  • Total Noise Level Reduction, TNLR: Total Noise Level Reduction illustrates the reduction of ambient noise level. The average level is above 5dB. Theoretically, higher TNLR would be better, but an over high result may be caused by severe attenuation of voice signal, or interruption caused by poor phone signal or noise reduction algorithm flaw.
    Signal-to-Noise Ratio Improvement, SNRI: capability of an NS method to enhance the speech component of a noisy speech signal from an additive background noise. SNR improves after noise reduction by comparing noise-reduced and raw voice signal. Generally, the improvement is over 4dB.
    SNRI-to-NPLR difference, DSN: the signal level difference between raw and noise-reduced. Noise reduction process would attenuate voice signal level, cell phones would gain signal to ensure the call quality. Theoretically, it would be best that signal level remain the same before and after noise reduction. A standard signal level peak is -2.5dB. If the signal was gained too high, overflow would happen, and that means frequent crackle, too low, voice signal strength would not be enough, and that means the sound would be too low, and the other end would not hear clearly.
    The result is just a test reference under similiar circumstances or conditions, third-party websites or official technical data cannot be used for comparison.

The 4 microphone sampling really helps, the result of Mate 9 proves that it has an excellent noise reduction performance on both handholding and hand-free mode, and significantly better than P9 that we were satisfied. Occasionally, small cracks may occur when we are using under handholding mode. The overall noise reduction performance is satisfied; we can hardly hear ambient noise even at hand-free mode.

Mate 9 supports directional audio capture in hand-free mode and video recording. Users can touch the microphone icon on the up right to switch it on. This feature utilizes the main microphone for speech sampling and the others for noise reduction. In extra-noisy scenes such as factories and bars, this feature is quite helpful. Huawei really made efforts on call quality for Mate 9.

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