: 1.Max sound output:110±5dB 2.Sound gain: ≥30dB 3.Total harmonic wave distortion: ≤10% 4.Input noise: ≤40dB 5.Voltage:d.c.1.5V 6.Current: ≤4mA1 unit of ear sound amplifier1 instruction manual3 units of earplug of different size