This article stems from a recent client request. The client asked me, as a professional engineer, to review and approve an acoustical test, an STC test, performed and reported by someone else. The municipal building inspector required the test report to bear the seal of a Professional Engineer (P.Eng.).
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I declined the request. A professional engineer’s seal is not simply an indication that the engineer has reviewed a document. By affixing the seal, the engineer assumes professional responsibility for the document's engineering content. Since I did not perform or supervise the STC test and could not independently verify all aspects of the testing procedure and results.
Hiring an unlicensed acoustical consultant
Many building owners, developers, architects, and contractors assume that anyone with a sound level meter can perform acoustical testing and sound transmission testing. Unfortunately, this misconception can lead to expensive delays, rejected permit applications, and the need to repeat testing.
One of the most common problems occurs when a building owner hires an unlicensed acoustical consultant or technician to perform Sound Transmission Class (STC), Apparent Sound Transmission Class (ASTC), or Noise Isolation Class (NIC) testing for a new residential development.
A Common Scenario for acoustical testing
Imagine a developer has completed construction of a multi-unit residential building. Before occupancy, the municipality requires evidence that the walls and floor-ceiling assemblies meet the applicable sound insulation requirements of the building code.
To save money, the developer hires a technician who advertises "acoustical testing" services. The technician performs field measurements and prepares a report stating that the building complies with the required sound insulation rating.
The developer submits the report to the municipality.
Problems with unqualified acoustical testing
Several days later, the municipality rejects the report because it was not prepared by a qualified professional authorized to provide engineering services required for the permit application.
The developer now faces several problems:
Why Does an Invalid Acoustical Test Happen?
In many jurisdictions, measurements alone are not sufficient.
Determining whether a building complies with building code requirements involves more than operating specialized equipment. Acoustical testing requires professional judgment, including:
These activities may constitute the practice of professional engineering in the Ontario jurisdiction.
A Sound Level Meter does not make someone an Acoustical Consultant. Modern sound analyzers can automatically calculate STC, NIC, ASTC, and other ratings. However, the instrument does not determine whether the test was conducted correctly or whether the results are suitable for demonstrating code compliance.
What does an acoustical consultant do?
Experienced acoustical consultants understand issues of acoustic testing such as:
These factors can significantly influence the reported rating. This article explains more about the acoustical consultant's role.
The Lowest Price Can Become the Highest Cost
Choosing the lowest-priced acoustical testing service may appear to save a few hundred dollars. However, if the report is rejected, the project may incur:
The total cost can easily exceed the savings from hiring an unqualified provider.
Questions to Ask Before Hiring an Acoustical Consultant
Before retaining someone to perform acoustical testing or sound transmission testing, ask:
A reputable consultant should be able to answer these questions clearly.
The Bottom Line
Sound transmission testing is more than collecting measurements—it is a professional evaluation of building performance. When the results are required to demonstrate compliance with a building code or to support a permit or occupancy application, the qualifications of the individual performing the work can be just as important as the measurements themselves.
Before hiring an acoustical consultant based solely on price, verify that they are qualified to provide the professional services your project requires. Spending a little more at the outset can prevent costly delays, repeated testing, and unnecessary frustration later.
