OPPO R11 Review: Call Quality
Author:Soomal
Source:eng.soomal.com

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OPPO R11 is the best seller for now. It comes with the latest Qualcomm Snapdragon 660, and the same dual camera with iPhone. This 2999-RMB smartphone was just OPPOish in our display and audio review. Will it be better in call quality?

The Qualcomm Snapdragon 660 processor is the latest in 6xx series, which brings "Kryo 260" CPU cores to the midrange. Qualcomm does not note whether the CODEC exists, or what the CODEC chip is. What we know is it is able to output 4W power. The Snapdragon 660 supports 2x2 MU-MIMO 802.11ac and Bluetooth 5, and features a Snapdragon X12 LTE Modem, paired with the new SDR660 RF transceiver, which support peak downlink data rates of 600Mbps to the 600-tier lineup of SOCs for the first time. As a smartphone that have to be sold in China mainland, dual-SIM-standby is necessary, but R11 has different versions, so the baseband may vary. This review is based on our R11 with all wireless work supporting.

R11 has a neat call function, but still including the Number Locator and Crank Call Identification that you need in China. By now, most smartphones have reliable hand-holding call performance, while the hand-free mode still need to be improved. R9s' awful performance really astonished us last year, R11 should and must be better. As usual, 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. And we use WeChat, the most popular tool in china, as VoIP. Then use professional sound card and microphone for recording and analysis.

Earpiece Speaker Test

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. Then use professional sound card and microphone for recording and analysis.

Testing Item OPPO R11 OPPO R9s Galaxy S8+ Huawei Mate 9 Pro vivo Xplay 6 iPhone 7 Plus
Output Level of Earpiece,dB -9.51 -11.5 -10.2/-9.98 -11.88 -10.56 -8.06

R11 has an ideal earpiece volume, much higher than R9s'. However, the sound quality does not change too much, just a fuller and coarser bigger 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 R11 OPPO R9s Galaxy S8+ Huawei Mate 9 Pro vivo Xplay 6 iPhone 7 Plus
Face Up,dB 75.6 78.7 73.4 74.1 78.1 78.9
Face Down,dB 74.6 77.0 73.7 77.7 78.3 79.8
In Camera Bag,dB 69.8 69.4 69.1 73.1 70.0 73.3

Because R9s is a bigger one, it is able to contain more audio components, R11 is not as good as R9s.

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[R11 Hand Holding] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 40.7 33.9 40.4 42.0 31.1
SNR Improvement,dB[Higher is Better] 27.8 25.7 28.6 30.8 20.3
SNRI-to-NPLR difference,dB[-4 to 3] -2.6 -0.5 -3.8 -3.7 0.9
Testing Item[R9s GSM Hand Holding] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 45.0 31.8 44.6 46.4 35.9
SNR Improvement,dB[Higher is Better] 34.8 23.6 37.7 36.1 23.3
SNRI-to-NPLR difference,dB[-4 to 3] -3.0 0.6 -4.1 -4.4 -0.7
Testing Item[R11 Hand-Free Mode] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 11.8 16.1 15.0 17.1 19.4
SNR Improvement,dB[Higher is Better] 8.1 12.5 6.7 9.2 9.0
SNRI-to-NPLR difference,dB[-4 to 3] -4.0 -2.4 -6.7 -5.7 -0.7
Testing Item[R9s Hand-Free Mode] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 43.5 33.2 41.3 46.4 31.5
SNR Improvement,dB[Higher is Better] 26.2 25.0 25.9 24.0 18.0
SNRI-to-NPLR difference,dB[-4 to 3] -15.4 -1.8 -17.6 -19.9 -0.8
Testing Item[VoIP] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 44.7 39.9 46.7 44.9 32.8
SNR Improvement,dB[Higher is Better] 31.9 27.9 36.5 33.8 26.7
SNRI-to-NPLR difference,dB[-4 to 3] -1.4 -0.3 -2.3 -2.3 2.2
  • 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.

R11 remains the same level in hand-holding mode, and makes big progress in hand-free mode, only if it can reserve more voice details in noisy circumstance. R11 reaches its limit in VoIP test. However, consider VoIP had developed stable voice quality and noise reduction technology, a normal mic is able to provide fair experience in WeChat, Skype or other VoIP apps. In summary, R11 has an average call quality, and improves the hand-free mode, providing practical value for driving or voice conference.

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