iPhone 8 Review: Call Quality
Author:Soomal
Source:eng.soomal.com

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iPhone 8 Plus comes with the latest A11 Bonic processor designed by Apple, 5.5-inch FHD IPS display, and dual cameras. Let's have a look at the sub-flagship's call quality.

It can be learned from iFixit that their iPhone 8 Plus adopts Qualcomm X16 LTE baseband. The A1864 sold in China mainland supports most wireless network, of course, single standby as usual, besides, iPhone 8 Plus also supports Bluetooth 5.0 and 802.11AC MIMO fast Wi-Fi network.

Apple adds lots functions for specific users from iOS 11, for example Color Filters for the color- blindness, as well as Phone Noise Cancellation switch. The internal phone app is able to call via VoIP, at the same time, you can choose the cellular, for example, to 2G to ensure the stability of calls. Lots users complained about the cracking earlier, our iPhone 8 Plus had fixed this problem by updating.

Earpiece Speaker Test

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.

Testing Item iPhone 8 Plus vivo X20 vivo X9s Plus OPPO R11 Galaxy S8+ iPhone 7 Plus
Output Level of Earpiece,dB -8.8 -10.1 -10.15 -9.51 -10.2/-9.98 -8.06

iPhone 8 Plus's earpiece output volume is slightly lower than 7 Plus, but still higher than most Android smartphone, and voice sounds full and transparent. Cracking is not significant after updating, but it sounds crude at the maximum volume occasionally.

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 iPhone 8 Plus vivo X20 vivo X9s Plus OPPO R11 Galaxy S8+ iPhone 7 Plus
Face Up,dB 78.4 78.8 78.1 75.5 73.4 78.9
Face Down,dB 78.2 80.1 78.2 75.8 73.7 79.8
In Camera Bag,dB 72.6 72.8 70.0 69.4 69.1 73.3

Earpiece for one channel, the stereo loud speakers in iPhone 8 Plus sounds wider in dynamic and higher in treble resolution.

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[Hand Holding] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 40.3 38.6 47.2 45.8 42.1
SNR Improvement,dB[Higher is Better] 32.2 18.5 28.6 32.9 20.4
SNRI-to-NPLR difference,dB[-4 to 3] -1.8 0.0 -3.7 -3.2 -0.1
Testing Item[Hand Free] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 17.2 18.5 28.6 32.9 20.4
SNR Improvement,dB[Higher is Better] 14.0 16.5 18.6 20.5 16.1
SNRI-to-NPLR difference,dB[-4 to 3] -2.6 0.4 -5.9 -4.8 0.4
Testing Item[VoIP] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 19.5 17.1 25.3 27.4 21.6
SNR Improvement,dB[Higher is Better] 16.4 17.6 19.5 23.2 20.1
SNRI-to-NPLR difference,dB[-4 to 3] -1.4 1.0 -3.4 -2.6 1.7
  • 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.

In hand-holding mode, iPhone 8 Plus is at the same level with iPhone 7 Plus, while in hand-free mode, iPhone 8 Plus gives us a little surprise, for better noise reduction and voice continuous. But it is unexpected that its recording volume is a little low in VoIP, which shoule be the best, such as Skype. In addition, iPhone 8 Plus is more stable in calls, as it never drops when we are using. Overall, iPhone 8 Plus made some progress in loud speaker and noise reduction, and the VoIP should be some bugs in app.

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