By Sally Moore
Sound will play a key role in the coming decade as aging baby boomers look to home building materials that block unnecessary outdoor noise. An aging population, combined with the economic reality of smaller lot sizes, government regulations forcing intensification, as well as the increasing prevalence of attached homes and condominiums means that the need for effective sound barriers from neighbours and neighbourhood noise will only increase.
“When it comes to smaller lots the problems will always be ‘the neighbours’,” said Don Campbell, a Canadian real estate expert. “But there are many new building technologies that suppress sound; even though they can cost more, they are worth it in the long run as they become a real selling feature.”
Campbell, a real estate investor and researcher who’s written four best-selling books about the industry, predicts that noise will become a major issue for home buyers over the next 10 years. Compounding the issue within single-family neighbourhoods, he adds, is the absence of any type of “condo rules” that impose sound restrictions and the fact that police today have little time to enforce noise complaints.
For condo owners, especially in high-density urban areas, not only can neighbours be a problem, but so too can the ongoing clamour of outside noise, from planes and trains to garbage trucks, sirens and vehicular traffic.
Do You Hear What I Hear?
Every municipality has different regulations. The City of Toronto, for example, defines “noise” as unwanted sound, and its acceptable level is typically a personal preference. However, there are several elements that determine one’s response to sound. Our perception of noise is affected by factors such as our mood, time of day, background noise and our expectations.
Outside “airborne sounds” reach the ear on the inside of a dwelling by entering through roofs, doors, cracks, windows, floors and walls. “Impact sound,” on the other hand, results from foot traffic, dropped or sliding objects, and travels through construction materials, primarily floors and ceilings.
Overall, sound energy travels through air, water or solid objects. Sound vibrations strike the eardrum and cause it to vibrate initiating the process we call hearing. The greater the pressure level that a sound wave exerts when it strikes a surface, the greater its sound level, measured in decibels (dB).
The “sound insulation” of a wall is that property which enables it to restrict the passage of noise or sound from one side to the other. “The rule of thumb in wall sound insulation is, simply: the more mass per area, the better the sound insulation,” said Jack Prazeres, president of MasonryWorx, a trade association representing brick, block and stone masonry professionals. In contrast, “sound absorption” is that property of a material that permits sound waves to be absorbed into a wall.”
Standards for Managing Sound
There are a number of ways to assess building materials for their ability to manage sound:
1. Sound Transmission Class (STC)
The National Building Code of Canada uses Sound Transmission Class (STC) to gauge the ability of floors and walls to isolate sound as it moves between the exterior and interior of a building and between living units in a multi-unit structure. STC rates a product’s ability to withstand the transfer of airborne sound at a specified frequency range and is equal to the number of decibels a sound is reduced as it passes through a material. Generally, the higher the STC rating the more noise that is blocked.
2. Outdoor–indoor transmission class (OITC)
Outdoor–indoor transmission class (OITC) is a standard used for indicating the rate of transmission of sound between outdoor and indoor spaces in a structure. While STC is based on a noise spectrum targeting speech sounds, OITC utilizes a source noise spectrum that considers frequencies down to 80 Hz (Aircraft/Rail/Truck traffic) and is weighted more to lower frequencies.
Noise Reduction Building Tips
For construction industry professionals there are a number of ways to reduce outside noise, improve quality of life and increase property values for your home or condominium buyer. These include:
1. Use the high SCT (Sound Transmission Class) and Outdoor–indoor transmission class (OITC) rated products. Make it a habit of asking about sound ratings when choosing building materials, and work these sound ratings into your marketing materials. It’s not all necessarily in the walls either; in the case of flanking or indirect paths, external noise can actually bypass high mass wall material and transmit through low quality floors.
2. Masonry products—block, brick and stone—perform exceptionally well in blocking low-frequency, airborne noise such as plumbing, heating and air conditioning systems, elevators, amplified music, traffic and aircraft. The high mass-per-area of masonry products provides superior sound control because it resists the passage of airborne noise.
For multi-units buildings, concrete block dividing walls can significantly reduce noise from neighbouring units as can concrete and block floors and ceilings. In most provinces, mid- and high-rise condos are mandated to use masonry or concrete for dividing walls and floors for fire safety purposes; but in low-rise condos (four storeys or under) and townhouses, using masonry or other high STC rated dividing walls and floors can help reduce outdoor sounds and noise from neighbours.
3. Triple-pane versus double-pane windows also often help to reduce noise levels. The type of insulation chosen is also an important consideration to reducing outside noise. Again, the density of the insulation is a key factor to reduce airflow and noise. Stone wool products have higher density and because the fibre is non-directional, they provide good sound barriers.
4. Acoustical doors are important for locations requiring greater sound isolation. Sound control doors are much heavier than conventional doors and can attain significant STC levels. The associated frames and hinges are built to support the additional weight, and particular attention is paid to the design of the perimeter seals. Where space permits it, a second suite door enclosing a vestibule can significantly reduce the noise between the corridor and the suite in condominiums.
5. Room placement can also mitigate sound. “A trend towards having the master bedroom suite in the basement will also become more prevalent in the years to come as the population seeks a quieter living space,” said Campbell.
Ideally, the design should include silent floors installed above, great ventilation, good light, fireplace and high ceilings. For outdoor spaces, consider building a courtyard design, which provides not only visual privacy, but acoustical privacy as well.
Sally Moore is the executive officer at MasonryWorx, the trade association of brick, block and stone masonry industry professionals committed to providing home buyers, homeowners, architects, engineers and builders with accurate, timely information about the use and benefits of brick, block and stone products.