The aluminum alloy tuning fork is not only a convenient string instrument tuning tool, it can also help you relax yourself, relieve anxiety, refresh your mind, and enter a deep meditation state faster, we will equip wooden speakers to make the reverberation last longer, the unique metal frequency of the tuning fork can enhance peoples ability to recognize sounds and improve their hearing.(The frequency error of tuning forks is within ± 5. All tuning forks are strictly tested with instruments before leaving the factory. The mobile phone audio measurement app does not measure accurately. If you have any questions, Please let us know.)