Subclause 6.3.3.2 – Volume of auditory ALARM SIGNALS and INFORMATION SIGNALS

ü For the OPERATOR to identify the onset or presence of ALARM CONDITIONS by means of auditory ALARM SIGNALS, those signals need to be audible above the background noise level and different from other sounds.

ü High background noise levels can mask or conceal the presence of auditory ALARM SIGNALS to such an extent that the OPERATOR can fail to hear them. Conversely, an auditory ALARM SIGNAL can be excessively intrusive or startling if its level is very high in relation to the background noise level. The OPERATOR might then seek to inappropriately disable or deactivate the ALARM SYSTEM.

û In any PATIENT care environments where the background noise level is known and constant, a fixed auditory ALARM SIGNAL volume can be reasonable.

העוצמה יכולה לעזור כאינדיקציה לדרגת החירום

ü The volume level of such a fixed auditory ALARM SIGNAL should exceed the background noise level to such an extent that it will be reliably detected but not to such an extent that it would be excessively startling or intrusive. Clinical experience has shown that values between 45 dB and 85 dB can be reliably detected without being too intrusive in most situations.

ü In many PATIENT care environments the background noise level is not constant. In operating rooms the background noise can vary from 50 dBA to 85 dBA. Additionally, one type of equipment can be used in several different kinds of PATIENT care environments; for example a ventilator that can be used in the home, in the intensive care area or for PATIENT transport.

ü Given the wide range of possible background noise levels in all possible PATIENT care environments, the committee did not consider it appropriate to specify any absolute volume level or range of levels for auditory ALARM SIGNALS.

ü Designers of ALARM SYSTEMS should therefore be aware of the typical background noise level (and how variable it can be) in the intended environments of use.

M ALARM SYSTEMS that are to be used when background noise levels are variable should be provided with means for manual adjustment of the auditory ALARM SIGNAL level or should automatically adjust the auditory ALARM SIGNAL level so that the perceived loudness remains the same despite changes in background noise levels.

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ü Because louder sounds are generally perceived to be more urgent, lower priority auditory ALARM SIGNALS should not be louder than higher priority ALARM SIGNALS.

ü If higher priority auditory ALARM SIGNALS are much louder than lower priority signals, they can be startling or intrusive. A reasonable compromise is for HIGH PRIORITY auditory ALARM SIGNALS to be approximately +6 dB louder than MEDIUM PRIORITY auditory ALARM SIGNALS, with an acceptable range from equal in volume (0 dB) to a maximum of +12 dB louder.

ü MEDIUM and LOW PRIORITY ALARM SIGNALS should be equal in volume, but if they are different, MEDIUM PRIORITY auditory ALARM SIGNALS should not be more than 6 dB louder than LOW PRIORITY auditory ALARM SIGNALS.

? It should be possible to adjust the volume level of auditory INFORMATION SIGNALS (e.g., pulse oximeter “beeps” or the “in-use” indicators on electro-surgical units) and the volume level of auditory ALARM SIGNALS independently, so that both can be set to appropriate levels.

שוב – השאלה אם ה- Information Gignals הם הכרחיים? או שעדיף מנגנון אבטחת שמיעה

ü If the volume levels of auditory ALARM SIGNALS and auditory INFORMATION SIGNALS are not independently adjustable, then INFORMATION SIGNALS should have no greater volume level than LOW PRIORITY auditory ALARM SIGNALS, and both should have lower volume levels than those of MEDIUM PRIORITY and HIGH PRIORITY auditory ALARM SIGNALS.

ü The auditory INFORMATION SIGNAL should be non-intrusive, non-startling and discontinuous in nature.

ü The volume (and range of adjustment of volume, if provided) of auditory ALARM SIGNALS in an ALARM SYSTEM are required to be disclosed to the OPERATOR so that the OPERATOR will be able to determine if the volume of the auditory ALARM SIGNALS is appropriate for the intended environment of use.

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