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How to Choose the Right 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 on 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 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.

Below is an example of the type of waveform 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

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.

AS06608PS-R with 1W, 520 Hz square wave
Microphone spaced at 10cm from test baffle		 AS04508MR-3-R with 1W, 325 Hz square wave
Microphone spaced at 10cm from test baffle

AS04004PO-R with 1W, 325 Hz square wave
Microphone spaced at 10cm from test baffle

AS02808MR-R with 1W, 325 Hz square wave
Microphone spaced at 10cm from test baffle

 

 

 

From our testing, we can deduce the characteristics of a speaker that makes it an ideal candidate to use within a Medical Device that needs to meet the criteria set forth by IEC 60601-1-8.

Steps to selecting the ideal speaker for your application:

1. Reference IEC 60601-1-8 to ensure correct tone selection for your product. Below is an example of tonal requirements* for different product applications.

Cause Medium Priority High Priority Mnemonic Notes Examples of type of Alarm System
General C C C C C C – C C Fixed Pitch Other Alarm Systems that do not readily fall into one of the following categories, including but not limited to electrical or non-oxygen gas supply systems, EEG monitors, intracranial pressure monitors, laparoscopic gas insufflation systems, calf compressor systems, etc.  Optionally this sound is permitted for the Alarm System of any kind of equipment.
Cardiac c e g c e g – g C Trumpet call; Call to arms; Major chord Anesthesia workstations that include cardiac monitors, multi-parameter monitors which include cardiac monitors, heart rate monitors, invasive or non-invasive blodd pressure monitors, cardiac output monitors, peripheral perfusion monitors (plethysmographs), transesophageal echo, fetal heart rate monitors.
Ventilation c a f c a f – a f Inverted major chord; Rise and fall of the lungs Anesthesia workstations which include ventilators (but which do not include cardiac monitors); lung ventilators, spirometers, CO2 monitors, ventilator disconnect (airway pressure) monitors, etc.
Oxygen C b a C b a – g f Slowly falling pitches; Top of a major scale; Falling pitch of an oximeter Pulse oximeters, transcutaneous / tissue oxygen monitors, oxygen analyzers, oxygen concentrators, oxygen gas supply lines.
Drug or Fluid Delivery C d g C d g – C d Jazz chord (inverted 9th); Drops of an infusion falling and “splashing” back up Volumetric infusion pumps, syringe drivers, anesthetic agent delivery systems or analyzers.
Equipment or Supply Failure C c c C c c – C c Falling or dropping down Any device when it experiences loss of power or other major failure of the device.

2. Convert the tones into their respective frequency. Use this musical note to frequency conversion chart to assist you.

3. Based upon the lowest musical note’s frequency (where C4, or middle C, would be ~261 Hz), you would start filtering for speakers with a resonant frequency of 261 Hz or lower.

4. If you need to meet a target SPL—70 dB at 1 meter is a good rule-of-thumb—you would then additionally filter for speakers that can achieve that SPL while observing the speaker’s power rating.

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.

Recommended Speakers

PUI Audio is the go-to speaker source for medical applications. Decades of experience in assisting the world’s leading Medical Device manufacturers allows us to recommend the following speakers for IEC 60601-1-8 devices:

Hi Fidelity & Superior Frequency Response:

Part Number Dimensions (in mm) Resonant Frequency SPL @ 10cm at Rated Power SPL @ 1m at Rated Power
AS02704MS-N50-LW100-R 27L x 27W x 6.6H 350 Hz 96 dB 76 dB
AS03204MS-3-R (4 ohm)

AS03208MS-3-R (8 ohm)

 32.7L x 31.7W x 16.5H 200 Hz 101 dB 81 dB
AS03604MR-N50-R 36D x 18H 200 Hz 103 dB 83 dB
AS06004PS-R (4 ohm)

AS06008PS-R (8 ohm)

 66.8L x 66.8W x 26.5H 160 Hz 109 dB 89 dB
AS09208AR-R 92D x 44.6H 90 Hz 112 dB 92 dB
AS03608AS-R 36L x 36W x 16.8H 250 Hz 98 dB 78 dB
AS05308AS-R 53L x 53W x 34H 230 Hz 108 dB 88 dB
AS06504PS-X-R 65.0L x 65.0W x 36.7H 130 Hz 111 dB 91 dB

Lead-Wired and/or Enclosed for Ease of Use:

Part Number Dimensions (in mm) Resonant Frequency SPL @ 10cm at Rated Power SPL @ 1m at Rated Power
AS02008MR-LW152-R 20D x 3H 500 Hz 93 dB 73 dB
AS02808MR-LW152-R 28D x 5.2H 500 Hz 95 dB 75 dB
AS03608MR-LW100-R 36D x 4.6H 500 Hz 101 dB 81 dB
AS04004PO-2-LW152-WR-R 40L x 28.5W x 11.7H 420 Hz 100 dB 80 dB
ASE04508MR-LW150-WP-R 45L x 36W x 20H* 420 Hz 98 dB 78 dB
AS06608MR-LW152-R 66L x 66W x 12.5H 380 Hz 101 dB 81 dB
AS07104PO-LW152-R (4 ohm)

AS07108PO-LW152-R (8 ohm)

 71L x 41W x 25H 250 Hz 104 dB 84 dB
ASE06008MR-LW150-R 60L x 30W x 10.3H* 300 Hz 101 dB 81 dB

*Denotes speaker with enclosure

Rugged and Durable for Element Resistance:

Part Number Dimensions (in mm) Resonant Frequency SPL @ 10cm at Rated Power SPL @ 1m at Rated Power
AS04004MR-N50-WP-R 40D x 21.5H 160 Hz 105 dB 85 dB
AS04504PS-X-R 45.4L x 43.3W x 29.2H 170 Hz 110 dB 90 dB
AS05804PS-X-R 58.3L x 55.3W x 33.8H 140 Hz 109 dB 89 dB
AS04004PO-2-WR-R 40L x 28.5W x 11.7H 420 Hz 106 dB 86 dB
AS04004PR-WR-R 40L x 40W x 17.5H 180 Hz 104 dB 84 dB
AS04008PS-4W-WR-R 40L x 28.3W x 11.5H 380 Hz 101 dB 81 dB
AS06608PS-WR-R 66.3L x 66.3W x 29H 230 Hz 115 dB 95 dB
AS07104PO-LW152-WR-R (4 ohm)

AS07108PO-LW152-WR-R (8 ohm)

 71L x 41W x 25H 250 Hz 104 dB 84 dB