Recording with the iPhone 11

The iPhone 11 that I used for this experiment has three stereo microphones — one for phone calls (bottom), one for videos (next to the camera), and one for Siri (next to the ear speaker). Overall, reviews for the recording capabilities of the iPhone 11 are decent. The phone seems to have a pretty flat frequency response curve, excluding very high ranges. Like most devices, midrange resonances can mess up the recording quite easily, however. To my knowledge, these microphones can record at a maximum sample rate 48kz at 32-bit depth and have both mono and stereo recording abilities. For a more in-depth review of the iPhone 11 and its cousins, follow this link: https://www.dxomark.com/apple-iphone-11-audio-review/#:~:text=Like%20the%2011%20Pro%20Max,of%20bass%20impaired%20the%20sound.

The Application:

My search for a “lossless” recording application that also allowed the disabling of auto gain balance was not easy. Previously, I had regularly used Voice Memos for recordings, because I wasn’t too concerned with the audio quality at the time. Voice Memos automatically compresses audio recordings for better storage, but by navigating to the audio quality settings in General settings, one can switch on “lossless.” That being said, Memos records in mono, and there is no convenient way to regulate the Auto Gain Control. Other applications, such as Dolby On, allow lossless, uncompressed, 16-bit recordings, but seem to have various gain balancing and tone balancing technologies. I finally chose Auphonic, an application that allows users to select between the three iPhone microphones, as well as select the sample rate, bit depth, and input gain. By default, Auphonic rids all IOS preprocessing.

Recording:

I did all my recordings with the bottom microphone at a sample rate of 48khz with 24-bit (the max) precision. I used my computer speakers to project both the sine and white noise files.

My experiment included six recordings total — three for sine sweep and three for white noise. Throughout my six trials, I experimented with both room size and microphone distance from the output source. For the first two recordings of each sound, I recorded in my room at two distances — one foot away from the source and four feet away from the source. The final trial for each sound is recorded in my common room, when the microphone is 15 ft away.

FREQUENCY RESPONSE GRAPHS:

Sine Sweep

WHITE NOISE

Results:

Although there are many differences between all three White Noise recordings, some patterns established themselves. For all three recordings, The microphone didn’t really pick up any frequencies between the 200-300Hz range. The extremity of this trough seems to have been exaggerated as I moved the microphone further away from the output source.  For all three recordings, there is also a trough at the 3000-6000Hz range and a peak at 7000Hz. One can also see that my iPhone won’t capture frequencies well past 20000Hz. The good news is that the dB difference between the loudest and softest frequencies remains about the same.

There are also some recognizable patterns among the three sine wave recordings. Like the white noise recordings, there is a loss of frequencies in the 200-300hz range. There is another trough in the 700ishHz range for all three and the peaks all occur at the same frequency. On top of that, the dB difference between the loudest and softest frequencies remained similar at different distances.

From my observations, I am convinced that my iPhone 11 has a fairly flat frequency response. I am somewhat convinced that although my microphone may exaggerate the lack of 200-300hz frequencies, the problem originates from my poor computer speakers, rather than from my iPhone mic. It is also generally the case that my frequency response curves were more flat the closer to the source I was.