Adjust volume to the minimum before wearing.<br />Increase volume gradually to avoid sudden increase in sound.<br />Convenient for watching movie， enjoying the drama， attending meeting， or having class， it could help you hear the sound clearly and loudly.<br />Max Sound Output: 130dB ± 5dB<br />Harmonic Wave Distortion: ≤5%<br />Frequency Range: 300-4000 hz<br />Input Noise: ≤30 dB<br />Battery: AG3<br />Working Voltage: dc1.5V<br />Working Current: ≤4 Ma<br />Measurement: 45x32x90mm<br />Net Weight: 8g<br />Notice:  Battery no included