The HA20 can amplify sounds both indoors and outdoors by 40dB, with a maximum audio output of 128dB and a frequency range of 200-5000Hz. The HA20 works on a button cell battery which is included and replacement are easily available. A battery is provided so you can enjoy the benefits of your new hearing amplifier for longer. The Beurer HA20 is presented in a useful velvet storage box, to keep your Hearing Amplifier safe when not in use.