Model LK128 Standard Features: √ Attractive design, small and light. √ Less noise, fine fidelity and tone. √ With volume adjustment switch. √ With ON/OFF switch. √ Tested according to International Standard IEC118-7. Specification: Max Sound Output: 128±5dB Sound Gain: ≥38dB Total Harmonic Wave Distortion: ≤10% Frequency Range: 400----4500Hz Input Noise: ≤30dB Voltage: 1.5V Current: 10.8mA Battery: AG13 Button Cell Estimated Battery Life: 35 hours