vivo X23 Review: Call Quality
Author:Soomal
Source:eng.soomal.com

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Vivo X23's screen notch has changed from a bang to a water droplet, still maintaining a high screen ratio. The new screen design and new processor make a clear difference of the X23 than the X21 half a year ago. What is the performance of voice calls and noise reduction?

The X23 is equipped with the Qualcomm Snapdragon 670 processor, which is basically an improved version of the Samsung 10nm FinFET process of the Snapdragon 660. The performance of this stage of the semiconductor process has been extremely limited, so the main advancement of the 670 is still in enhanced architecture and AI. The Kyro360 CPU has up to 2.0GHz, ISP supports dual 16MP camera, and the improved AIE smart engine.

In terms of communication, the Qualcomm Snapdragon 670 integrates the X12 baseband, up to LTE+ 600mbps downlink rate, supporting mainstream commercial 3G and 4G bands, and the X23 supports dual card dual standby and single 4G standby switching. X23 also supports Bluetooth 5.0 and 802.11ac, running the Funtouch OS system based on Android 8.1. Voice call and noise reduction test still use China Mobile 4G, China Unicom 2G, VoIP uses Wi-Fi network for testing.

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 vivo X23 OPPO Find X OnePlus 6 Galaxy S9 Huawei P20 Pro vivo X21 iPhone X
Output Level of Earpiece,dB -11.52 -11.21/-9.95 -9.38 -8.58 -8.66 -9.4/-10.08 -8.36

The earpiece on the top of the X23 needs a little closer observation. In general, if the sounding cavity is juxtaposed directly above the camera, it is obviously not enough to open the hole. In fact, the X23 earpiece is slightly to the right of the center at the top, when moving in calls, you will notice the difference in volume. From the output volume, the X23 is slightly smaller than the X21, but the performance is still sufficient for daily use. The performance is more general in terms of voice quality, and there is more obvious burr and stiff feeling under the highest call volume.

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 vivo X23 vivo X21 OPPO Find X vivo NEX S OnePlus 6 Galaxy S9 Huawei P20 Pro iPhone X
Face Up,dB 78.7 77.7 78.7 78.0 74.1 74.3 76.8 78.5
Face Down,dB 78.7 78.2 76.9 79.5 74.2 75.4 74.6 78.6
In Camera Bag,dB 73.1 72.0 74.1 73.3 69.2 69.4 69.6 72.2

The X23's laud speaker volume is slightly better than X21, but the gap is very small. There is no obvious change in sound quality and sound style. The volume is large enough to avoid call missing, the sound is slightly thin, and it is still a regular mono design.

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.

In the VoIP test, we encountered a strange problem, the voice output recording has an irregular delay between each sentence interval of the standard recording signal, about 50 milliseconds or more, the same situation after repeated test, signal, network and other issues excluded. Although this will not have a significant impact on the call, but cannot pass the timeline for comparison of the ITU test scoring program, the current mobile phone's own noise reduction processing will not have such a significant delay, which is generally the cloud There is a bug or software problem in the server, which is not related to the mobile phone, so this result is not recorded.

Testing Item[Hand Holding] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 42.7 41.5 48.5 48.5 32.5
SNR Improvement,dB[Higher is Better] 36.2 31.3 41.6 39.6 16.6
SNRI-to-NPLR difference,dB[-4 to 3] -2.4 0.4 -3.2 -4.1 1.5
Testing Item[Hand-Free] Noisy Crowd Background Music Pink Noise Roadside Voice
Total Noise Level Reduction,dB[Higher is Better] 24.4 15.4 42.2 45.8 21.1
SNR Improvement,dB[Higher is Better] 17.5 19.0 31.4 29.1 13.1
SNRI-to-NPLR difference,dB[-4 to 3] -4.1 3.1 -7.1 -4.6 3.5
  • 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 the handheld mode, the X23 has a good filtering on the background sound of music, but the effect of vocal processing is more general. In hands-free mode, X23 can basically maintain a good call quality, and only occasionally some voice loss occurs under the intense pink noise. The noise reduction performance of the roadside and the interior of the car is acceptable. The X21 has better noise reduction in the handheld mode, and the noise filtering is cleaner, but the X23 voice will be clearer and the hands-free performance is basically the same. After all, X23 is somewhat different in terms of call and noise reduction, but there is no difference in overall level.

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