Choosing the Right IEC IEC 60601-1-8 Speaker

How to Choose the Right IEC 60601-1-8 Speaker

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 of the alarm signals and should be referred to as the ultimate reference with regards to the specific tones to use in your device, there are three main requirements that pertain to speaker selection:

1. A pulsed frequency between 150 Hz and 1 kHz
2. At a minimum of four harmonics of the pulsed frequency between 300 Hz and 4 kHz
3. 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.

Which Specifications Are Most Important

PUI Audio has taken the performance criteria called out by IEC 60601-1-8 and performed studies on speakers to gauge which specifications stand out as most important when selecting speakers to meet the criteria. Each test below was performed with the speaker mounted to a test baffle, and a B&K measurement microphone connected to a Listen, Inc. SoundCheck test system set to spectral analyzer mode.

Speaker Integration Best Practices

If possible, mount the speaker to the inside face of the outer housing. This maximizes the speaker’s measured output. Leave a keep-out area of at least 3mm between the speaker’s diaphragm and the surface in front of it.

Ensure that the speaker is mounted in such a way to create a seal along the outer edges of the speaker’s frame. This reduces cancelation that occurs if the front of the speaker’s diaphragm/cone can interact with the back of the diaphragm/cone. Cancelation can cause a reduction in output below 1 kHz.

As the signal to the speaker is a trapezoidal waveform, or a square wave, power handling needs to be calculated using the formula below. Do not exceed the rated power (not the maximum instantaneous power, which is meant for use with voice or music) of the speaker.

Power = (Volts peak)2 / Impedance

Exceeding the speaker’s rated power will cause damage over time. Typically the type of damage will be broken voice coil tinsel leads or a burned voice coil that causes open load resistance, or a deformed voice coil former which locks the voice coil in the magnetic motor.

Mounting the speaker within an enclosure will improve performance at and below the resonant frequency of a speaker. Please contact PUI Audio for more information regarding the correct enclosure volume for your application.

If your application will be chemically cleaned in a hospital environment, choose a speaker that has been treated (our WR series speakers) or a speaker with a Mylar or aluminum diaphragm.