By Eric de Santis, P.Eng.
Troubled condo-owners often ask me “does the noise I can hear in my apartment exceed the limits allowed under the Building Code?”
..the intention of the National Building Code of Canada (which is the model for all provincial codes) is to provide the minimum provisions acceptable to maintain the safety of buildings.
Before I answer this question, it is important for the reader to first understand that the intention of the National Building Code of Canada (which is the model for all provincial codes) is to provide the minimum provisions acceptable to maintain the safety of buildings. There is little to no risk of immediate injury or death resulting from the experience of noise in a building. As such, the acoustic requirements of the Building Code are much less onerous than those related to the structural, mechanical and electrical integrity of a building.
The NBCC does not provide any requirement to control the level of noise in buildings. Instead, it provides a minimum specification for the separating partitions ability to block sound transmission between dwellings. The general public typically calls this soundproofing. Acoustic engineers call it airborne sound insulation. By specifying a minimum sound insulation standard, the Building Code helps to control “airborne” noise transmission between suites. Noise sources that are airborne in nature include human voices, babies crying, dogs barking, televisions and audio systems.
..the developer has not necessarily provided a “good” or “high” level of sound insulation between dwellings..
It is important for condo owners to be aware that by building a separating wall or floor that meets the Building Code minimum requirement, the developer has not necessarily provided a “good” or “high” level of sound insulation between dwellings. Consequently, the level of sound insulation experienced by owners may not be commensurate with their expectations, especially if they bought their condominiums in the belief that they were buying into a high-end or luxury development. Neither will building a separating wall or floor that meets the Building Code minimum requirement protect an owner from noise transmission resulting from a floor layout that positions a noisy room of one suite (i.e. living room) next to a quiet room of the adjacent suite (bedroom).
The Building Code relates only to the control of airborne sound transmission. However, noise disturbance can also be experienced through the process of “structure-borne” noise transmission. This occurs where the fabric of the building is struck by an impact, such as a plate dropped on hardwood floor or furniture dragged across a floor, or where mechanical or electrical equipment such as pumps, air-handling equipment, transformers or elevators impart continuous vibration into the structure.
The Building Code contains no provision for controlling structure-borne noise.
The Building Code contains no provision for controlling structure-borne noise. It does, however, recommend a minimum level of impact sound insulation for the floor assembly. Complying with this recommendation will help reduce structure-borne noise transmission from footsteps, dropped objects and dragged furniture, but will do little to reduce the impact of building services equipment. Although these issues are not addressed by the Building Code, noise control measures can be included during the design phase of the development. However, many developers do not address these issues quite simply because there is no regulative requirement to do so.
Having said this, some developers do go the extra mile by specifying that noisy equipment be vibration isolated, and by selecting separating partition assemblies in excess of the Building Code requirement, particularly where the condominiums are marketed as “high-end” or “luxury”. BAP Acoustics has worked with clients seeking to provide a higher quality product in terms of the level of sound insulation achieved between suites. We have worked with other clients to develop uprated separating floor assemblies designed to provide a high standard of impact sound insulation, although there is no requirement to do so under the Building Code.
Before buying an apartment, do your homework and evaluate your expectations. Do you want the apartment to just look nice, or do you want it sound just as good as it looks? Ask your realtor or developer about the acoustic design standard of the building and confirm that they go beyond minimum requirements.
Written by Behzad Haki, B.Sc. and Eric de Santis, P.Eng.
You are sitting in a restaurant surrounded by some of your best friends. The food is great and the drinks are cold. The restaurant is gradually getting busier. Between the chatter and the background music, you begin to raise your voice to be heard by those at your table. You are not alone in this. Almost everyone else is doing the same. The background chatter gets louder and louder as everyone in the room also raises their voice to be heard. This is the Lombard Effect: the tendency for humans to raise their voice in the presence of noise.
The background chatter gets louder and louder as everyone in the room also raises their voice to be heard. This is the Lombard Effect: the tendency for humans to raise their voice in the presence of noise.
While it is hard to know the extent to which a noisy eating environment can adversely affect a business, noise can be a major concern for certain customers and owners. In some restaurants, a loud environment is preferred so that the customers will be discouraged from spending too much time in the space. However, there are other restaurants in which a relaxing ambient environment is preferred. Nevertheless, in an eating space under normal conditions, most of the time, the customers want to be able to verbally engage in conversation with their companions. As a result, regardless of the type of a restaurant, the acoustic characteristics of the space should be such that customers do not need to over exert themselves when speaking.
As a result, regardless of the type of a restaurant, the acoustic characteristics of the space should be such that customers do not need to over exert themselves when speaking.
In an eating space, building services, background music, and most importantly, human-related activities such as talking, make the greatest contribution to the ambient noise level. The amount by which a source contributes to the ambient noise level is controlled by two factors: reverberation time (RT), and loudness of the source.
Reverberation time is a measure of the time it takes for sound to decay by a fixed amount (60 dB). If reverberation time is high, it takes a relatively long time for an unwanted sound to dissipate from a space. As a result, in spaces with high RTs, high levels of ambient noise can be expected if there are enough noisy activities taking place in the room. Moreover, louder noise sources create more ‘unwanted’ sounds that also result in high levels of ambient noise.
It is the ratio of a desired sound (the conversation to be conveyed) to all unwanted sounds that specifies how easily a conversation is audible. If the level of unwanted sounds is high, then to have a relatively acceptable audible conversation, one must speak louder. However, in a shared environment like a restaurant, speaking louder introduces more unwanted sounds for people who are not part of that conversation.
The above two way relationship, essentially puts a limit on the number of patrons who can occupy an eating space such that the ambient noise level will not exceed tolerable levels. However, if the ambient level is too high, reducing the number of occupants in order to achieve a better quality of verbal communication would be an unacceptable option for most restaurant owners. A better option would be to decrease the ambient level by decreasing the room’s RT (i.e. make the room less reverberant so that the room can get rid of unwanted sounds faster than before). This can be achieved by the addition of sound absorptive materials to available interior surfaces (i.e. walls, ceiling, floors, seats etc.).
However, some practical concepts, such as Acoustical Capacity, exist for the purpose of acoustic design and evaluation.
Now, the question is how much reverberation is allowable in a space with a certain number of patrons. Unfortunately, unlike many other types of interior spaces (e.g. lecture halls, theatres, classrooms), there is not much literature available on the desirable acoustical performance standards of eating spaces. However, some practical concepts, such as Acoustical Capacity, exist for the purpose of acoustic design and evaluation.
Acoustical Capacity of a space is defined as “the maximum number of people allowed in a room for ’Sufficient’ quality of verbal communication” . Acoustical Capacity is dependent on the volume of an eating space and the reverberation time (RT):
There are basically two ways to interpret the above equation. To reach a desired number of occupants in an eating space without compromising speech audibility, either the reverberation time must be decreased (as already explained) or the volume must be increased (which is usually not a practical solution).
Figure 1: 3D model of a restaurant with no acoustical treatment
To illustrate the benefit of an Acoustic Capacity upgrade, consider the example of the restaurant shown in Figure 1. The restaurant eating space consists of a wood ceiling, a polished concrete floor, and steel stud gypsum-board cavity walls. The restaurant has a floor area of 1776sqft (165m2) and a ceiling height of 13ft (4m). We built an acoustic model of the restaurant using AFMG’s Enhanced Acoustic Simulator for Engineers (EASE). With standard hard reflective walls, floor and ceiling, the room has a model predicted RT of 1.2s (when occupied) and an Acoustical Capacity of 25 people.
Figure 2: 3D model of a restaurant with acoustical treatments on walls and ceiling
As shown in Figure 2, sound absorptive treatment was added to the ceiling and walls in the model. As a consequence, the RT was reduced from 1.2s to 0.5s. The Acoustic Capacity of the room was increased from 25 to 66 people.
The acoustic model was also used to auralize the untreated and treated space. You can listen to the demo files below to appreciate the difference. Headphones are strongly recommended!
Clip 1: Speech and background chatter in the untreated restaurant
Clip 2: Speech and background chatter in the treated restaurant
In short, with a few careful acoustic improvements, a restaurant can be more hospitable for customers (even without encouraging them to stay longer times than usual). Moreover, in some cases, the owner can be able to increase the room capacity without compromising the comfort of the customers. If you are an owner and you want to find out more about our services, contact us by phone at 604.492.2992, or by filling out our online form.
 Rindel, Jens Holger (2012). Acoustical capacity as a means of noise control in eating establishments. Joint Baltic –Nordic Acoustics Meeting. link: http://www.odeon.dk/pdf/C116-BNAM_2012_Rindel_29.pdf
Written by Eric de Santis, P.Eng.
Speech privacy is critical aspect of office acoustics, particularly as it relates to boardrooms and meeting rooms. Many office discussions are best conducted behind closed doors, but how can you know if an eavesdropper is able to listen to your discussions? To provide guidance on this acoustics engineering issue, ASTM International Standard E2638-10 defines five levels of speech privacy/security for enclosed meeting rooms and offices (see table).
For minimal or standard speech privacy (Levels 1 & 2), we aim to control the intelligibility of speech. In this situation, an outside listener can potentially hear speech sounds, but would have some difficulty understanding the conversation. For speech security (Levels 3 to 5), we aim to control both the intelligibility and audibility of speech.
Two key factors determine the intelligibility and audibility of speech from a closed room: the sound attenuation provided by separating partitions and the background noise level at a potential listening point outside of the closed room. Sound attenuation refers to the degree by which sound is reduced from within a source room (e.g. a meeting room) to listening positions outside the room. Background noise, such as that provided by an HVAC system, can reduce the intelligibility/audibility of speech through sound masking.
Both of these factors, sound attenuation and background noise, must be carefully considered in the control of speech between adjacent office spaces. As an example, let’s consider a boardroom that is separated from an adjacent cellular office by a typical single-stud cavity wall (filled with batt insulation) with one layer of gypsum wallboard on either side. To minimize costs, this hypothetical wall has been installed up to a suspended T-Bar ceiling. The background noise environment within the office is controlled by the HVAC system. The noise level in the office is 35dBA (i.e. a quiet office). Under these conditions, a minimal level of speech privacy should be expected (Level 1).
We have two ways to increase the speech privacy between these spaces to Level 2. The first is to continue the wall to the underside of the ceiling (assuming there are no other sound attenuation weaknesses). The second is to increase the level of noise in the office space by using a sound masking system.
Many open offices employ a sound masking system for this purpose. The output of such systems must be carefully configured. Too low in volume, and the masking system may fail to provide sufficient masking. Too high, and there is a risk of increasing worker annoyance and lowering productivity. Generally speaking, background noise levels in an open office should not exceed 45dBA. In a cellular office, a 40dBA background noise level is more suitable.
To achieve a standard level of speech security (Level 3) in the above example, both the introduction of a sound masking system and building the wall from slab to slab would likely be required. Significant changes in wall construction would be required to achieve the higher speech security of Levels 4 and 5.
This example is a simplified case. In reality, there are many ways in which the sound attenuation of speech from an office to the potential listening positions outside the room can be compromised. These include window/wall junctions, penetrations through walls, interconnecting doors, and shared HVAC ducts between adjacent spaces. We call sound transmission via these indirect paths “flanking transmission”. With this in mind, the best time to address noise control is at the design stage of the office, when we can review the client’s privacy/security requirements and then work with the architect to develop partition assemblies and design junction details to control flanking transmission.