What to Know Before Calling an Acoustical Consultant to Deal with a Noise Problem
Complaints may be related to a noisy neighbor or adjacent amenity area, or a next door commercial business such as a fitness centre or restaurant/bar, but noise also commonly emanates from a steady or intermittent source of often unknown origin, which may be outside, or somewhere deep within a building.
Contributing noise factors
Two key factors contribute to a noise’s sound level at the point of complaint: the sound power generated at the source and the path and distance the noise takes from the point of origin. Sound and vibration energy can travel long distances, in all directions from a source, through air, water or structurally via material objects such as building frames, pipes, and ducts. Airborne sounds, travelling as air pressure waves, can come into living or work spaces through small hidden gaps and openings found around piping, ductwork and electrical junctures. Noise can also penetrate through solid floor/ceiling assemblies and the structure that extend between living, working, common, and service areas. This can be a problem when the unwelcome sounds of fitness centers, pet grooming clinics, bars and restaurants, childcare centers, dental clinics and the like flank wall and ceiling sound barriers and find their way into noise sensitive spaces such as a residential bedroom, a commercial spa, or a corporate boardroom.
Assessing reasonable limits based on typical noise standards
Noise complaints do not necessarily always suggest a deficiency or problem. Some audible noise from building services, or adjacent units is considered normal for a typical multi-unit residential or commercial building, and does not necessarily warrant the implementation of noise control measures. Before getting into potentially complicated (and potentially expensive) investigations, in some cases, it may be worth first having an acoustical consultant determine if the noise in question is beyond reasonable sound transmission limits based on typical standards for residential or commercial buildings. Unfortunately there are no criteria set out in the building code or other statutory documents for commercial spaces in relation to sound levels or sound transmission. It is often up to the discretion of the developer, the property management, and the limits and restrictions set out in tenant lease agreements to determine whether a noise problem should be remedied or not.
Acoustical test and measurement between adjacent units
An acoustical consultant can measure the sound levels or the sound transmission properties and evaluate against typical standards or lease agreements (see page on STC and IIC Testing). In residential buildings airborne sound transmission limits are set by the building code where the limits are expressed as STC ratings i.e. STC 50 (The higher the number, the better the sound isolation). In tenant lease agreements or condominium documents the limits can be expressed as STC and/or IIC ratings i.e. STC 50/IIC 55).
As often as not, an acoustical assessment will find that the walls or floor assemblies tested meet building code criteria or other relevant targets. The building code criteria for sound transmission limits of walls and floors is sometimes lower than an occupant’s expectations for quiet, leaving many tenants disbelieving that the code does not support their contention and frustration. Code compliant wall and floor assemblies often provide sound insulation that is good for high frequencies, reasonable for mid frequencies and generally fair to poor for the lower frequencies. What this means is that voices, being higher frequency, are typically not heard or are unintelligible, but an entertainment sub-woofer’s deep, low frequency rumbles can penetrate barriers and be heard despite the wall or floor being to code.
Addressing noise intrusion issues as part of a lease agreement
Many of these potential problems can be anticipated and addressed for mitigation as part of a lease negotiation. In the case of a fitness centre looking to potentially open in a residential or commercial building, an acoustical engineer could create scenarios in order to assess the potential for sound and vibration intrusion from typical activities of the proposed fitness center into adjacent tenant spaces. These scenarios can involve using an audio PA system in the proposed spaces to recreate the rhythm, amplitude, and frequency content characteristics of a typical cardio workout class, including the music program played during the exercise routines. Similar conditions can be created in current fit-outs of spaces proposed to be the aerobics room, and weights/treadmill areas.
With regards to vibration caused by aerobic activity or structurally-transmitted vibration impacts in the weights and treadmill areas, analysis can indicate the requirements for suitable floor slab stiffeners and isolated flooring to mitigate perceptible vibration in adjacent spaces.
The potential for audible structure-borne noise from these type of activities can be difficult to predict, therefore, best practices for flooring systems is typically recommended. This entails an appropriate resilient underlay below a subfloor (usually wood, but sometimes concrete is required), upon which the surface flooring of choice may be used (usually sports rubber flooring). This technique has proven to be very effective in isolating fitness spaces in buildings with “sensitive” tenant or condominium neighbors.
Once the analysis is completed, an acoustical engineer can provide these kind of mitigation design recommendations for incorporation into a lease agreement to ensure that noise and vibration would not, under practical circumstances, intrude on other spaces.
Investigating building equipment noise and vibration intrusion
Mechanical equipment found on rooftops and in mechanical penthouses can also create vibration which, in turn, can radiate down into a building’s structure and occupied spaces.
If the source is not properly vibration-isolated, the building’s structure can transmit the vibrations internally, where it can radiate elsewhere as structure-borne noise. Building occupants could perceive this as a neighbouring noise problem, despite the fact that its originating source was vibration induced, and from a far removed, remote part of the building.
Potential sources of noise and vibration in these instances include HVAC systems; pumps, motors and chillers; backup generator sets; elevators; garbage chutes and compactors; garage doors; and the like. These common building services systems can be found in all areas of a building: on rooftops, in basements, and in the walls, ceiling, and mechanical rooms of any floor.
For example, during a recent investigation, an intermittent source of noise and vibration that was troubling a tenant was found to be emanating from the actions of cars driving over a speed bump depression in the underground parking garage several floors below. In another, an annoying tone heard in a suite was traced back via piping to a pump more than twenty floors above.
Keeping a noise or vibration log
Before calling in an Acoustical Consultant to investigate and evaluate an issue, it is often best to first keep a noise or vibration log that charts time, frequency and characteristics of noise or vibration occurrences. This should be logged by the complainant, but may also be maintained by Property Management who can then use the log to investigate whether there might be any corresponding occurrences far removed from or seemingly unrelated to the tenant’s location, which may in fact be the origin and cause of the noise or vibration issue in question. In any event, if an acoustical consultant is ultimately called in, the log data collected can jump start their investigations and can lead to a much quicker and potentially more economical assessment and if mandated, mitigation solution for the problem at hand.