S02: Maximum Noise Levels

(3 points)

INTENT

Establish background noise level criteria for enclosed spaces in order to promote best-practice HVAC and façade design techniques and ultimately bolster acoustical comfort within.  

SUMMARY

This WELL feature requires design- and performance-based compliance that projects can adhere to in order to facilitate comfortable interior noise levels. This feature can operate in tandem with Feature S01: Sound Mapping by introducing the specific performance thresholds for background noise levels within specified locations as attributed by internal and external noise sources.

ISSUE

A space that is negatively shaped by HVAC system and exterior noise intrusion can be described as either too loud or distracting. Both instances are individually problematic: the level of background sound may affect speech communication, audio features and, in extreme conditions, the effectiveness of public address systems. Studies indicate that employees are unable to habituate to noise in office environments over time, and office noise, with or without speech, can create stress and disrupt performance on more complex cognitive tasks (e.g., memory of prose, mental arithmetic). Background noise also poses a problem from a universal design and accessibility standpoint when the signal-to-noise ratio favors background noise over speech intelligibility, thus making it hard to engage in critical listening for the purposes of learning or performing tasks. In Europe, external noise intrusion from sources like transportation or industry have been linked to occupant annoyance in buildings. In adults, exposure to traffic noise can lead to complications with the cardiovascular system, diabetes, hypertension, stroke, depression and high blood pressure. For children, chronic aircraft noise exposure impairs reading comprehension, mental arithmetic and proofreading. In both industrial and community studies, road traffic noise exposure is related to raised catecholamine secretion levels in urine, indicating an increased stress level in subjects exposed to such noise. Increase in the use of light-weight construction materials has the potential to result in poor sound transmission performance across building façade elements.   

SOLUTIONS

Acoustical comfort can be impacted by noise emitted from HVAC systems. HVAC systems are ideally designed with the initial intent to meet specific Noise Criteria (NC) and in some cases can be retrofitted with acoustical treatment needed to meet sound pressure level (dBA) thresholds. Distracting and potentially harmful exterior noise can also be mitigated by providing façade elements that are most conducive to reducing outdoor noise transmission. While some retrofitting options exist for controlling exterior noise intrusion, exterior noise is most effectively treated during the design stages of a given space.   

IMPACT

Designing with background noise level criteria in mind is key to ensuring acoustical comfort across a range of project types. When exposure to noise is reduced, occupants are less susceptible to distraction, overall stress and potential health risk.

REQUIREMENTS

Part 1

Limit Background Noise Levels (Max: 3 points)

Verified by Performance Test

For All Spaces

The following is achieved:

1. Background noise levels do not exceed the thresholds below:

   Sound Pressure Level (SPL)		Open Workspaces, Dining Areas	Enclosed Offices, Residential Living & Sleeping Areas (Daytime)	Conference Rooms, Classrooms, Residential Sleeping Areas (Nighttime)	Points
   Average SPL (Leq)	dBA	45	40	35	3
   	dBC	70	65	60
   Max SPL (LMax)	dBA	55	50	45
   	dBC	80	75	70
   Average SPL (Leq)	dBA	50	45	40	2
   	dBC	75	70	65
   Max SPL (LMax)	dBA	60	55	50
   	dBC	85	80	75
   Average SPL (Leq)	dBA	55	50	45	1
   	dBC	80	75	70

Note:

1. L_eq measurements may exceed optimal levels by no more than a 4 dB tolerance.
2. L_Max measurements are slow-weighted and may exceed optimal levels by no more than a 9 dB tolerance.

© International WELL Building Institute