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

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This year, OPPO launched the Find X, the top automatic lifting mechanism design and the dual-edge-curved AMOLED screen brought a very high screen-to-body ratio, and it is also one of the most eye-catching domestic mobile phones this year. Soomal believes that many people have already made a choice between the NEX and Find X. Can Find X's performance on voice calls become a plus item?

Find X is equipped with Qualcomm Snapdragon 845 processor, supports dual card dual standby, covering of global TD/FDD 4G and 4G+ bands, and high-speed wireless network support such as Bluetooth 5.0 and 802.11ac. Find X's nanoSIM card holder is also chicer, made the front and back sides to control the area of the opening. Because it is an integral lifting mechanism, the Find X earpiece can use a conventional speaker unit, and the earpiece speaker at the top is transmitted to the user through the front panel hole at the top of the screen, at least in terms of volume, which is more advantageous than NEX's innovative flat-panel receiver. Of course, Find X's rise and fall of the front component will bring some differences that user will feel the difference in the volume of the handset. Find X runs the ColorOS 5.1 system. Since the 3.5mm headphone port is removed, users can only listen to music and make calls using Bluetooth headsets or various Type-C adapters. According to the convention, the objective test of voice calls is completed by China Mobile's 4G LTE and China Unicom GSM bands.

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 Find X OnePlus 6 Galaxy S9 Huawei P20 Pro vivo X21 iPhone X
Output Level of Earpiece,dB -11.21/-9.95 -9.38 -8.58 -8.66 -9.4/-10.08 -8.36

In the raised state, the output level of the Find X's earpiece is slightly higher than the stowed state. Of course, the earpiece sound of Find X is large enough in both states, and the tone is quite satisfactory. Press up at the maximum volume will enter the gain mode makes the sound brighter and sharper.

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 Find X vivo NEX S OnePlus 6 Galaxy S9 Huawei P20 Pro vivo X21 iPhone X
Face Up,dB 78.7 78.0 74.1 74.3 76.8 77.7 78.5
Face Down,dB 76.9 79.5 74.2 75.4 74.6 78.2 78.6
In Camera Bag,dB 74.1 73.3 69.2 69.4 69.6 72.0 72.2

Find X's loud speaker volume is also large enough, close to NEX performance, full of vocals, the burr at the maximum volume will be slightly more, because of mono, the sound field in the game and video experience may not enough.

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] 45.9 41.0 47.0 48.2 35.7
SNR Improvement,dB[Higher is Better] 38.2 33.6 41.7 40.6 27.1
SNRI-to-NPLR difference,dB[-4 to 3] -2.0 0.7 -2.9 -3.1 0.1
Testing Item[VoIP] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 46.2 30.4 47.3 47.9 36.1
SNR Improvement,dB[Higher is Better] 36.5 30.4 39.2 39.6 24.9
SNRI-to-NPLR difference,dB[-4 to 3] -1.8 0.7 -2.6 -2.3 1.1
Testing Item[Hand-Free] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 46.2 30.4 47.3 47.9 36.1
SNR Improvement,dB[Higher is Better] 36.5 30.4 39.2 39.6 24.9
SNRI-to-NPLR difference,dB[-4 to 3] -1.8 0.7 -2.6 -2.3 1.1
  • 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.

Find X's call noise reduction level in handheld mode did not bring any surprises. The ambient analog noise except the background vocal can be processed and filtered well, and indexes are excellent, and similar performance is obtained under VoLTE and common VoIP. In the hands-free section, Find X still retains the main part of the voice information, especially in the environment of the roadside and driving cars, the hands-free performance is slightly better than NEX. Overall, the overall call performance of Find X is in the mainstream of the same hardware configuration phone, and it is also the level of a 5,000 Yuan (about $750) mobile phone.

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