What is SoundExpert

SoundExpert (SE) is an independent non-commercial audio research project, which provides audio quality ratings of sound equipment and technologies such as mp3, aac, wma ... encoders and portable players (to be extended). It is the home for innovative music-based audio metric which works both for objective audio measurements and for listening tests. SE is in beta state because the new audio metric and corresponding listening test design are not widely adopted by audio engineers. So, please, use our ratings with caution.

The new listener-centric audio metric allows to perform objective audio measurements using real-life music material and various technical signals, not only sine waves. Such measurements:
• correlate well to human perception of sound quality
• are valid for digital audio
• do not contradict traditional audio metric but extend it
• are understandable to people without technical background
• can be performed at home using any recording device

The first practical application of the new measurement method can be found on the Portable players page.

The new listening test design helps to hear sound artifacts which are normally beyond threshold of human perception. The core of the new design is sound artifacts amplification technology (SARTAMP), which is backed by the new audio metric. Such amplification is particularly important for testing high-bitrate encoders and high quality audio equipment. This technology is used in SE listening tests since 2005. The tests are blind - participants don't know the particular device they assess. Resulting quality scores are completely unbiased and free from marketing and advertising noise.

The ratings of encoders are computed in real time while participants of the listening tests send their grades to the rating system. The more participants - the more devices and technologies can be tested. The testing procedure is simple and short enough that anyone, including you, can participate. Just download a test file (<3Mb), listen it (<15s) and send back your grade. Details are in the test file. The more accurate grades - the more reliable ratings.

Detailed but still easy to understand overview of SE distributed listening tests is in the paper Live Listening Tests @SoundExpert.

The main idea behind SoundExpert project is consumer control over sound quality of various audio equipment and technologies on the market. Production side deserves clearly defined feedback from consumers.

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Audio quality of Xiaomi Redmi 6A

Published Date 5/28/19 11:00 AM

Recording of SE test sequences, played back by Xiaomi Redmi 6A smartphone Why not to test some modern entry-level smartphone? What audio quality could we expect? Xiaomi Redmi 6A - around $100. Let's see.

Figure 1. Recording of SE test sequences, which include both technical signals and various music material (the test set "Variety"). Processing of these records results in standard df-measurements presented on Fig.2 below.

Df-slide showing location of various test signals (including 2 hours of music) on Df scale according to their levels of degradation

Figure 2. Df-slide with audio measurements of Redmi 6A. Df-slides of other devices can be compared with each other on the Portable players page.

Almost all technical signals are reproduced by the smartphone more accurately than by many devices tested to the moment. Not surprising that real music signal also shows low Df level (the Median, -27.1dB). Artifact signature of Redmi 6A is very close to Shanling M2s (Fig.4) and six out of ten tech.signals have better Df levels with Redmi 6A, including the Median. For sure, Redmi 6A sounds as good as dedicated Hi-Rez. M2s, at least with 32 Ohm headphones. It looks like high quality sound is a standard feature now in smartphones.

Conclusion:

Audio quality of Xiaomi Redmi 6A is in line with top smartphones. Amaxing.

Appendix

*All-off*
1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31	32	33	34	35

-30.4	-26.0	-25.6	-33.4	-26.8	-27.3	-32.3	-26.2	-24.2	-24.3	-29.9	-25.5	-26.5	-28.0	-35.5	-27.5	-34.3	-26.5	-33.5	-38.9	-31.7	-24.1	-26.5	-21.4	-28.2	-26.3	-23.7	-20.6	-26.5	-26.7	-26.6	-20.8	-34.3	-26.7	-28.4

Figure 3. Diffrograms of 35 tracks of the test set “Variety”, played back through Redmi 6A. They show level of waveform degradation of the musical signal divided into 400ms chunks (one pixel each, max. degradation is Red). Median Df values of the tracks are indicated. Click a track to open in full size for quick comparison with similar tracks from another device. More about diffrograms → Diffrogram: visualization of signal differences in audio research.

Figure 4. Dendrogram showing similarity of artifact signatures of tested players. The shorter the link between two players, the more similar their artifact signatures.

Dendrogram showing similarity of artifact signatures of tested players

**Table 1**. Underlying matrix of Spearman distances between artifact signatures for the dendrogramm. The Spearman distance = 0.1 is critical for relation of Df measurements to subjective scores. For the players that have similar artifact signatures (distance < 0.1) their perceived sound quality correlates well to df-measurements performed with substantial amount of real-life music material (histogram medians).
	`(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)`
`(1) Apple iPad mini 2 (2) HTC Desire C (3) HTC Desire C (ba) (4) Shanling M2s (5) Shanling M2s (HighGain) (6) Shanling M2s (gradual) (7) Apple A1749 adapter (8) OnePlus 6 (9) Apple iPod 5th (Video) (10) Xiaomi Redmi 6A`	0 0.0619 0.0972 0.0445 0.0446 0.0334 0.0374 0.0111 0.0578 0.0318 0.0619 0 0.0655 0.0149 0.0147 0.0174 0.1494 0.1029 0.0017 0.0286 0.0972 0.0655 0 0.0651 0.0651 0.0660 0.1710 0.1306 0.0612 0.0712 0.0445 0.0149 0.0651 0 0.0002 0.0024 0.1378 0.0887 0.0112 0.0103 0.0446 0.0147 0.0651 0.0002 0 0.0025 0.1379 0.0888 0.0110 0.0106 0.0334 0.0174 0.0660 0.0024 0.0025 0 0.1229 0.0752 0.0140 0.0081 0.0374 0.1494 0.1710 0.1378 0.1379 0.1229 0 0.0095 0.1455 0.1135 0.0111 0.1029 0.1306 0.0887 0.0888 0.0752 0.0095 0 0.0988 0.0689 0.0578 0.0017 0.0612 0.0112 0.0110 0.0140 0.1455 0.0988 0 0.0235 0.0318 0.0286 0.0712 0.0103 0.0106 0.0081 0.1135 0.0689 0.0235 0