What is SoundExpert

Audio metric that makes a differenceSoundExpert (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.

Live Listening Tests @SoundExpertThe 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.

 

 

Articles

« Back

Audio quality of iPod 5th Generation (Video)

Audio quality of iPod 5th Generation (Video)

Published Date 5/17/19 11:30 AM

Recording of SE test sequences, played back by Apple iPod 5th Gen.This audio player is from 2005. Like almost all portable players by Apple it was remarkable for its audio quality and usability. Many early iPods are still in use and can be easily found on eBay. Such well-known “anchor” players from the past are important points on the global AQ map, SE is trying to build.

 

 

 

 

 

 

 

 

 

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 the iPod. It can be compared with Df-slides of other devices on the Portable players page.

 

Artifact signature of iPod 5th differs substantially from modern audio solutions by Apple. Sine 1kHz is distorted 10dB higher than sine 12.5kHz. Relative position of triangle signals on Df scale indicates that odd harmonics prevail in the distortions. Almost all tech. signals with this iPod show worse Df levels than with modern ordinary spartphones. High output impedance. Definitely this device has noticeable sound character.

Conclusion:

Thanks to Wolfson audio chip with relatively high level of waveform degradation iPod 5th (Video) has its own distinctive sound signature (slightly harsh mids, transparent highs). Some music types/genres can benefit from this artifact signature, some other will not. As a result there always be lovers and haters of this player. Starting from iPhone 4 and iPod 6th Gen. Apple uses much more transparent/neutral audio chips from Cirrus Logic. High-Ohm headphones are recommended for this iPod 5th.


 

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
iPod 5th - Variety - 1 iPod 5th - Variety - 2 iPod 5th - Variety - 3 iPod 5th - Variety - 4 iPod 5th - Variety - 5 iPod 5th - Variety - 6 iPod 5th - Variety - 7 iPod 5th - Variety - 8 iPod 5th - Variety - 9 iPod 5th - Variety - 10 iPod 5th - Variety - 11 iPod 5th - Variety - 12 iPod 5th - Variety - 13 iPod 5th - Variety - 14 iPod 5th - Variety - 15 iPod 5th - Variety - 16 iPod 5th - Variety - 17 iPod 5th - Variety - 18 iPod 5th - Variety - 19 iPod 5th - Variety - 20 iPod 5th - Variety - 21 iPod 5th - Variety - 22 iPod 5th - Variety - 23 iPod 5th - Variety - 24 iPod 5th - Variety - 25 iPod 5th - Variety - 26 iPod 5th - Variety - 27 iPod 5th - Variety - 28 iPod 5th - Variety - 29 iPod 5th - Variety - 30 iPod 5th - Variety - 31 iPod 5th - Variety - 32 iPod 5th - Variety - 33 iPod 5th - Variety - 34 iPod 5th - Variety - 35
-20.6 -16.7 -16.0 -23.2 -16.7 -17.3 -22.5 -16.3 -14.2 -14.3 -20.0 -15.5 -18.2 -17.8 -25.6 -18.0 -24.5 -16.4 -23.3 -28.8 -23.1 -14.7 -17.3 -11.8 -18.5 -16.9 -15.0 -11.2 -16.8 -17.6 -16.7 -12.0 -24.2 -17.2 -19.6

 

Figure 3. Diffrograms of 35 tracks of the test set “Variety”, played back through iPod 5th (Video). 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

 

It looks like average linkage for the dendrogram better reveals clusterization of players according to their artifact signatures. So it will be used instead of complete linkage from now on.

 

 

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)
 (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)		  0      0.0619 0.0972 0.0445 0.0446 0.0334 0.0374 0.0111 0.0578
0.0619 0      0.0655 0.0149 0.0147 0.0174 0.1494 0.1029 0.0017
0.0972 0.0655 0      0.0651 0.0651 0.0660 0.1710 0.1306 0.0612
0.0445 0.0149 0.0651 0      0.0002 0.0024 0.1378 0.0887 0.0112
0.0446 0.0147 0.0651 0.0002 0      0.0025 0.1379 0.0888 0.0110
0.0334 0.0174 0.0660 0.0024 0.0025 0      0.1229 0.0752 0.0140
0.0374 0.1494 0.1710 0.1378 0.1379 0.1229 0      0.0095 0.1455
0.0111 0.1029 0.1306 0.0887 0.0888 0.0752 0.0095 0      0.0988
0.0578 0.0017 0.0612 0.0112 0.0110 0.0140 0.1455 0.0988 0

 

 

 

By Serge Smirnoff
1993002 Views, 1 Comment
Flag
artifact signature audio quality ipod video sound signature
Average (0 Votes)
The average rating is 0.0 stars out of 5.
Comments
Add Comment
Nick A.
I've had a good luck having this phone the moment i got myself a pair of RevoNext RN-QT3. Purchase of player is kind of suspended. There is a guides in web easy to find, how to increase system max volume of Xiaomi devices, which works for this model, increasing it's max volume from 177 to 244 variable, effectively making this phone an outstanding hi-fi player.
Posted on 1/14/20 5:42 PM.
Audio-Transparency Initiative
All articles ►
Audio-Transparency Initiative