For those who may be interested, here are some early testing results of audio quality through the iPhone 4 in three different use models. In summary, handset performance is the most improved for both incoming and outgoing audio, with headphone port performance only modestly different, while speakerphone performance is better for the iPhone 4 user, but not as much to the person on the other side of the call.
Handset Performance. The most noticeable improvements on the iPhone 4 relate to its two speakers, which have both seen dramatic volume upgrades. In handset mode, the iPhone 4 at 9/16 of its volume is roughly equivalent to the iPhone 3G/3GS at maximum volume, so the iPhone 4 at peak volume is roughly 40-50% louder—an extremely noticeable difference. iPhone 4’s handset speaker sounds a little clearer than the ones in iPhone 3G and 3GS, even at higher volumes, for “very clear” overall sound that has roughly the same tonality as before.
iPhone 4’s noise-canceling microphone works properly and impressively in handset mode. During silences, the microphone sounds just a little clearer than with the iPhone 3G and 3GS, such that words are a little more distinct. However, iPhone 4 improves considerably when there’s ambient noise in the background. During an iPhone 3G test call, music playing loudly in the background could be heard during both gaps in speech and while the person is speaking; with the iPhone 4, the music was completely filtered out after only a couple of seconds, becoming all but impossible to hear during either gaps or speech, with only very slight clipping of the speaker’s voice—the caller can hear virtually everything perfectly. The effect is similar to the Jawbone series of headsets, only built right into the phone.
Headphone Performance. Sonic differences were very modest between the iPhone 3G and iPhone 4 when testing with the same pair of Apple Earphones with Remote and Mic. Audio sounded ever so slightly better on the iPhone 4, but not in a meaningful way. Notably, the iPhone 4’s second noise-canceling microphone doesn’t work as well when you use microphone-equipped headphones; trickles of ambient noise pop in and out both during silences and speech.
Speakerphone Performance. The iPhone 4 at 10/16 volume is roughly as loud as the iPhone 3G/3GS at maximum volume, and doesn’t suffer from the same audio clipping and harshness that the earlier speaker did at the peak volume level. At maximum volume, there’s a substantial difference—the iPhone 4 is roughly 40% louder, and still clearer than the iPhone 3G/3GS at its peak. Unfortunately, these improvements benefit only the person listening with the iPhone 4, while the person on the other side doesn’t get a huge benefit. Noise-cancellation with iPhone 4’s dual microphones doesn’t appear to work very well, if at all, in speakerphone mode; the iPhone 4’s mics pick up as much ambient noise as voice, making it difficult to discern one from the other. On the other hand, the iPhone 4 user in a noisy music-filled room can hear you talking if the iPhone 4 is at maximum volume, whereas the iPhone 3G/3GS are drowned out.
We’ll have much more to say on the iPhone 4’s test results soon.