Smartphone Audio Quality Testing
by Chris Heinonen on December 8, 2013 5:15 PM EST- Posted in
- Smartphones
- Audio
- Mobile
- Tablets
- Testing
Dynamic Range
The dynamic range of the phone indicates the difference between the loudest possible sound and the background noise. The more residual noise in the background, the lower the dynamic range. Phones with more powerful amplifier sections will typically produce a greater dynamic range. The residual noise level is often constant, so as the overall volume level increases the difference between the music and the noise increases as well.
The best performer here is the iPhone 5 again, with 92.214 dB of range. The worst is the Nexus 5 with only 89.332 dB. A difference of 3 dB is not something I would concern myself over. If we see a phone or tablet that drops down below 80 dB then I will start to show more concern.
Crosstalk
Crosstalk, like dynamic range, is just a number here. This is the measurement how much signal leaks from one channel into another. If an instrument should only be in the right ear, some of that signal will leak into the left ear, but we want that as low as possible. The results are expressed in -dB, or how much quieter one ear is than the intended ear.
On the Note 3 we see a wonderful crosstalk measurement of -117.2 dB so the sounds in one ear are -117 dB quieter in the other ear. This makes them impossible to hear. The worst is the iPhone 5, with only -75.624 dB of isolation.
Stepped Response
The stepped response uses a 1 kHz 0 dBFS tone but measures output level from maximum volume to minimum volume. We can see how large the volume steps are and how many there are. It doesn’t produce a number we can use, but it ties back into our other results. For a good example, we can look at the Note 3.
We see steps that are around -5 dBu each. The final level is muted and just the background noise of the device. Each step is clean and even but as we get lower and lower we see noise start to intrude. This is the background noise starting to become audible in the signal. The flatter the levels are, the quieter it will be. Now, let us look at the Nexus 5.
Notice at the very top how the right and left channels do not overlap. That is the clipping we talked about at the very beginning. It isn’t until the 4th volume setting that the level difference is down to nothing. Because of this, I would consider the top 3 volume settings of the Nexus 5 as ones that should be avoided. They each have enough THD+N introduced into them that it will sound poor, and one ear will be louder than the other.
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porphyr - Monday, December 9, 2013 - link
This article is fantastic. I love that you are going to be testing audio quality. Obviously testing anything takes a lot of time, but I think it would be nice to see how these phones perform at "reasonable" listening levels. It would be great if you could pick dB level that is pleasant through the apple earpods and test a 2nd time at that, sort of how you use 200 nits for panel tests. That would give a more helpful representation of performance. Another thing that I would really appreciate is an explanation of how bad (or good) performance needs to be for most people to hear the difference (with bad and with good headphones). Thanks for the piece.99sport - Monday, December 9, 2013 - link
Thanks for the great article.Can you add built in speaker testing? I have an HTC one, and while I prefer to turn beats audio off when I use my phone in the car (listening to music on the car's speakers), I much prefer the sound of the built in speakers with beats audio on. As others have pointed out, all of the pieces in the chain are important to sound quality. My guess is that the frequency response of the built in speakers is much less at low frequency, and the beats audio increase in gain shown in your chart (below 100Hz) is designed to compensate for the frequency response characteristics of the built in speakers. In other words, if you tested the frequency response of the built in speakers (using a microphone with a known linear frequency response to gather the data), would the curve be much flatter when using the built in speakers with beats audio turned on versus turned off? Would the HTC one with beats audio on in fact have a much better (flatter) frequency response through the built in speakers than other phones do through their built in speakers?
It would be very useful to be able to compare the sound quality of the whole sound reproduction chain including the built in speakers – for me, the built in speaker sound quality and volume level is a major discriminator between phones – right up there with display color accuracy and camera quality.
dishayu - Monday, December 9, 2013 - link
Excellent initiative. The HTC One frequency response looks dreadful. I'm looking forward to graphs with beats enhancement off.As the next step, I would really like to see where different types of audio devices compare to each other... smartphones, ordinary media players (ipods), audiophile media players (HM-801), entry level/top level PC sound cards, realtek onboard chipsets.
NeoteriX - Monday, December 9, 2013 - link
I'm not sure if it's necessary to go through the effort of including PC soundcards, motherboard solutions, etc., but including media/MP3 players would definitely be a nice addition. The place that mobile phones have now as media consumption devices in addition to being phones came as an evolution from the original media device.However, the media device, given its singular purpose, prominently had sound quality as a major review component, and consumers did look at the DACs and opamps used. When they evolved to all-purpose smartphones, suddenly there were a lot of other features that took precedence, including processing power, display quality, etc.
Now that AnandTech is shepherding in a new look at audio quality, comparing the state of mobile phones to the heyday of media device would definitely be useful.
stunta - Monday, December 9, 2013 - link
Excellent article! It would be fantastic to see results from commonly used mp3 players. iPod, Sandisk Sansa (Clip, Fuze etc.) etc.How do you feed the test tone into the phone? Does the Audio Precision device come with test files you simply drop on the phone and play?
Also, do we know if these phones use the same amplifier for the built-in speakers and headphone outputs?
Thanks again!
Impulses - Monday, December 9, 2013 - link
I'll second this and dishayu above, it'd be a great reference.Hell, if we could get you to test output of a few BT receivers out there that might also be interesting and valuable to readers... I know BT's another can of worms as it introduces more compression etc, but it's actually gotten quite decent and those receivers end up replicating (and thus bypassing) many of the same components in phones.
There's not a lot of in depth reviews out there for those things but seeing as you can use them with any pair of headphones they'd fit right into your testing and they can be a suitable solution/alternative to a phone's line out. Something like the older Sony MW-300, or the newer models, or three equivalent Samsung/LG models.
Panzerknacker - Monday, December 9, 2013 - link
Please test the Oppo Find 5! I use that phone and it should have good audio capability. Wonder how it does vs iPhone 5.juhatus - Monday, December 9, 2013 - link
Now if only apple would enable their audio tech (noise-cancel atleast) on bluetooth.I downgraded from nokia 800 to iphone5 and atleast using the in-car-bluetooth the audio on calls went really bad.
On other comment, the graphs are huge in this article, maybe little scaling or something? some bare flatlines there and very big size graphs.
Nice article :)
Impulses - Monday, December 9, 2013 - link
Great article, though I have a quibble with the headphones to be used for future testing... Nothing against either as I've owned both, and the SR80 are a fine candidate (common entry level open headphone recommendation). The AKG have a reputation for being hard to drive and they aren't exactly very portable anyway, plus they represent another dynamic open headphone. I think a popular IEM (Ety, Shure, even Apple's dual driver IEM) might be a better second alternative, if it's at all possible with your rig... I know IEM are a pain to test due to seal issues and whatnot. Failing that maybe some other dynamic headphone that's more likely to be used with a mobile device (V-moda M-80? Senn HD25-1 II?), or something cheap yet extremely popular and good for the $ (Koss Portapro or KSC75).Impulses - Monday, December 9, 2013 - link
Also, if you could test and report output impedance for the phones that would be a HUGE help for people trying to figure out what kinda headphone would work best... Relatively high output Z isn't uncommon and it can wreck havoc with some lower impedance headphones, particularly sensitive IEM (and specially the multi balanced armature models that are so prevalent now).