- Six different phones, including Apple, Android, and conventional phones, were tested to measure their ability to playback and transmit recorded white noise. - For playback, the iPhone 4 had the highest cutoff frequency of 15,564 Hz, while the LG enV 1 had the lowest of 3,470 Hz, indicating smartphones have better sound quality for playback. - However, for transmission between phones, all phones had similar cutoff frequencies close to 3,600 Hz, reflecting the standard telephone network transmission range of 300 Hz to 3,400 Hz.