Smartphone Audio Quality Testingby Chris Heinonen on December 8, 2013 5:15 PM EST
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We spend a lot of time watching and listening to our smartphones and tablets. The younger you are the more likely you are to turn to them for watching a movie or TV show instead of an actual TV. For a lot of us it is our primary source of music with our own content or streaming services. Very rarely when new phones or tablets are announced does a company place any emphasis on the quality of the audio.
Display quality also used to receive very little attention. As more and more people reported on the display performance, more companies started to take notice. Now benefits like “Full sRGB gamut” or “dE < 3” are touted on new products. So now we are going to introduce a new set of testing for smart phones and tablets, audio performance.
To do this right we went to the same company that all the manufacturers go to: Audio Precision. Based out of Beaverton, OR, Audio Precision has been producing the best audio test equipment out there for over 25 years now. From two channel analog roots they now also test multichannel analog, HDMI, Optical, Coaxial, and even Bluetooth. Their products offer resolution that no one else can, which is why you will find them in the test and production rooms of almost any company.
Just recently they introduced a brand new set of audio tests for Android devices. Combined with one of their audio analyzers, it allows us to provide performance measurements beyond what has been possible before. Using an Audio Precision APx582 analyzer we set out to analyze a selection of Android phones to see what performance difference we can find. More phones and tablets will follow as these tests can be run.
The Test Platform
The test platform is the Audio Precision APx series of audio analyzers. For this initial set of tests I used an APx 582 model, which has two analog outputs and 8 channels of analog inputs. The outputs are not necessary as all of the test tones are provided by Audio Precision for playback on the devices. For each set of tests we can add a load, simulated or real, to see how the device handles more demanding headphones. For this article I am sticking with only a set of the updated Apple Earbuds. They are probably the most common headphone out there and easy to acquire to duplicate testing. For future tests the other loads will be AKG K701 headphones and Grado SR60 headphones. Both models are popular, and I happen to own them.
There are a few main tests we are going to use for all these reviews. Those key tests are maximum output level, Total Harmonic Distortion + Noise (THD+N), Frequency Response, Dynamic Range (as defined by AES17), and Crosstalk. These tests are the exact same ones that manufacturers will be running to verify their products. Most of these tests will be run at maximum output levels. Most amplifiers perform best at close to their maximum levels, as the residual noise compared to the signal decreases, and so that is what they are typically tested at.
We might add more tests as we decide they are relevant to our testing. I will also attempt to go back and fill in as much data as possible from previously reviewed devices as time permits. Now to look at the tests and see our results for our initial set of phones.
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brusselwilson - Sunday, December 8, 2013 - linkIs sample variation an issue of relevance for smartphone audio systems?
cheinonen - Sunday, December 8, 2013 - linkNo more than it would be with anything else I would think. For the Nexus 5 I tested two different samples (one from Brian, one from a friend of mine) and both exhibited this issue. So you might see small variations, as you would with any display or anything else, but nothing major I wouldn't think.
vailr - Sunday, December 8, 2013 - linkAnother factor to consider: certain cell companies can enable enhanced audio quality for cell phone calls, but only on selected cell phone models. The IPhone 5 has that ability, as I recall. Not sure about the specifics, but I believe that both ends of the cell call must be using supported phones, as well as: the cell provider must enable that feature. That would enable cell calls to have better voice quality than land line calls, via increased audio frequency response.
shenkey - Sunday, December 8, 2013 - linkCould we also get Windows Phone devices included in the test. Lumia 920 and 1520 should fit in the range.
cheinonen - Sunday, December 8, 2013 - linkI'll add whatever I can when I get a chance. This first run has taken almost all my time up since the week of Thanksgiving.
hopfenspergerj - Sunday, December 8, 2013 - linkIt's not useful to measure noise/dynamic range at the highest volume setting. You have to measure at one of the lowest settings to determine whether the phone truncates bits, whether the noise floor does not decrease with the volume setting, etc.
I have an htc dna and it is completely, totally, utterly useless for playing music with sensitive IEMs; I suspect many android phones with "-90db" thd+n measurements are similarly bad in practice.
hopfenspergerj - Sunday, December 8, 2013 - linkNot to mention poor shielding on the dna causes the phone to output chirping and static and other loud extraneous noises whenever it transmits data.
cheinonen - Sunday, December 8, 2013 - linkWe have stepped output level charts as well that measure this, they just aren't included here right now. I can start to pull those out for current and future tests if we want to use them.
evonitzer - Monday, December 9, 2013 - linkI saw that one graph included when you compared the Nexus 5 and G2 at different levels and I think it should be in all the reviews. I always run my IEM's in the lower half of the volume range so I am quite interested in how they perform. As others have said, excellent work!
DoctorG - Tuesday, December 10, 2013 - linkSame here -- I always run my good IEM's below half volume at least (usually more like a third.) No point in having good headphones & music if the volume is turned up so loud it hurts....
BTW Great job Chris! I have always wanted more in-depth reviews about smartphone audio quality. It's very important to me, but so far there haven't been any reliable/objective tests available. Thanks! Just a thought, but maybe it would be possible to test against a pro-quality amp/DAC? When I use my GNex, the quality is obviously very different from my audio interface that I use with ProTools. It'd be interesting to see just how much of that is measurable...