With the increased use of medical electronics in medicine today, the International Electrotechnical Commission (IEC) developed the IEC 60601-1-8 standard to regulate alarm signals to prevent confusion, when several instruments are sounding at the same time in the same room.
While the IEC 60601-1-8 standard covers every aspect on the alarm signals and should be referred to as the ultimate reference with regards to the specific ones to use in your device, there are three main requirements that pertain to speaker selection:
- A pulsed frequency between 150 Hz and 1 kHz
- At a minimum of four harmonics of the pulsed frequency between 300 Hz and 4 kHz
- The sound pressure level (SPL) of the harmonics must be within +/-15 dB of the pulsed frequency
Additional pulse requirements - such as pulse duration, rise time, and fall time - are also part of this standard, but pertain more to the input signal sent to the speaker.
Below is an example of the type of waverform characteristics* that may be used to meet the IEC 60601-1-8 criteria. The flat portion of the waveform is used to create the harmonics from the fundamental pulsed frequency.
*For informational purposes only.
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