From an audio perspective, mobile devices are a challenge: Physical size limits the power they are able to feed the headphones, the listening environment is often noisy, and they are highly price-sensitive. We tested iPods, iPads and smartphones on a number of audio parameters.
The equipment used was “Otto,” a head and torso with fine, built-in condenser microphones, nearfield monitors, main monitors, a calibrated SPL meter and loudness software.
Otto was calibrated using pink noise at -23.0 LUFS to the nearfield monitors placed 240cm from the torso, giving an SPL of 77.0dB slow C per channel, 80dB for both, at Otto’s position. The 80dB SPL point was used as reference, and calibration was repeated twice per day.
Mobile devices were tested with several signals such as speech, music, pink noise and tones. For each test signal, its True-peak and Program Loudness value were read from the DUT’s display while playing. The main objective was to predict the SPL for a given Program Loudness when using headphones.