Have You Been Recently Asked to Perform a Transformer Sound Study?
As San Diego continues to grow and urban density increases, the demand for reliable, safe, and community-conscious infrastructure has never been higher. That includes electrical infrastructure—particularly transformers, which are essential for delivering power to homes, businesses, and public facilities. But with those transformers comes another, often overlooked, concern: sound.
If you’ve been asked by San Diego Gas & Electric (SDG&E) or another utility to perform a transformer sound study as part of your project approval process, you’re not alone. Soundproof San Diego has recently received inquiries from developers, property owners, and engineering firms who are navigating this requirement for the first time.
In this article, we’ll break down exactly what a transformer sound study is, why SDG&E and other utilities request it, and how our team can support you through the process.
What Is a Transformer Sound Study?
A transformer sound study is a type of acoustic assessment that measures and evaluates the noise produced by electrical transformers. These units emit low-frequency humming and buzzing sounds due to internal processes like magnetostriction, cooling fan operation, and vibration.
While often subtle, transformer noise can become a serious issue in residential neighborhoods, near sensitive commercial operations, or in mixed-use zones where people live and work close to the power infrastructure.
A transformer sound study generally includes:
On-site sound level measurements taken at varying distances and angles
Environmental noise assessments to determine how transformer noise interacts with ambient noise
Modeling and projections for future equipment or changes in site layout
Compliance analysis to ensure the installation meets city and utility noise regulations
The goal of the study is to determine whether the installed or proposed transformer complies with municipal noise ordinances and utility-specific acoustic thresholds—including those set by SDG&E.
Why Do Utilities Like SDG&E Require These Studies?
Utilities such as SDG&E have a responsibility to maintain positive relationships with the communities they serve while also upholding strict regulatory standards. Transformer noise can lead to:
Noise complaints from residents
Delays in construction or permitting
Negative press or reputational damage
Increased legal and engineering costs
To avoid these outcomes, utilities require sound studies as part of their pre-installation and post-installation compliance processes—especially in areas with:
Residential adjacency: When transformers are located close to single-family homes, multi-unit buildings, or other residential dwellings, even low-frequency humming can become disruptive. These settings often have lower allowable noise thresholds and increased sensitivity to ambient sound.
Mixed-use zoning: In developments that combine residential, commercial, and public functions, utilities must consider the diverse acoustic expectations of each space. What might be acceptable for a commercial loading dock could pose a serious concern just a few feet away in a residential or hospitality setting.
Sensitive receptors such as schools, hospitals, and care facilities: These institutions often house vulnerable populations who require quiet environments for health, learning, or recovery. Noise from transformers in these zones may trigger stricter compliance standards and greater scrutiny.
Environmental noise ordinances enforced by local or regional governments: Jurisdictions across California, including San Diego County, have adopted nuanced noise codes that dictate acceptable decibel levels by time of day, location, and zoning type. Projects must align with these codes to receive final approval.
If your project involves new utility infrastructure, retrofitting, or equipment upgrades, you may receive a request from the local utility company to conduct a noise impact assessment specific to transformer sound. This is especially common near:
Apartment buildings
Schools and universities
Commercial business parks
Hospitals and medical centers
Residential neighborhoods
We recommend checking with your city planner if you’re unsure whether this requirement applies to your site.
What Causes Transformer Noise?
Transformer noise primarily stems from internal components, including:
Magnetostriction: A physical phenomenon where the transformer’s core expands and contracts as alternating current flows through it. This generates a humming sound typically around 120 Hz.
Cooling Systems: Fans or pumps that activate when the unit reaches certain temperatures.
Mechanical Vibration: Movement of internal parts can cause casing vibration and low-frequency resonance.
These sounds can travel through open air or radiate through the ground and surrounding structures. Depending on the location and terrain, this can result in perceptible and disruptive noise levels several hundred feet from the transformer itself.
While modern transformers are designed with noise control in mind, not all installations account for the unique acoustic challenges of the surrounding environment. That’s why an objective noise control evaluation is so important.
Who Needs a Transformer Sound Study?
We most often assist:
Developers working on new residential or commercial buildings
Contractors and electrical engineers installing or relocating utility equipment
Property owners adjacent to utility easements or substations
Architects and planners preparing submittals for utility and city approval
If you are in the planning stages of any project involving SDG&E or another California utility, it’s a good idea to consult a sound expert early. Catching potential compliance issues ahead of construction can save months of delay.
What a Sound Study from Soundproof San Diego Includes
Our approach is tailored to both the technical requirements of utilities and the practical needs of developers and property owners. A typical transformer sound study includes:
Site visit and measurement
Assessment of existing ambient conditions
Clear reporting
Each situation is unique, and our role is to provide objective acoustic data and documentation that supports informed decision-making by project stakeholders.
Regulatory Considerations
San Diego and many other California jurisdictions enforce local noise ordinances based on:
Time of day (day vs night limits)
Zoning type (residential, commercial, industrial)
Decibel thresholds for sound levels
SDG&E may also have internal guidelines that go beyond municipal codes, especially when projects involve sensitive environments or high-risk exposure.
We help you understand the intersection between city code, CEQA (California Environmental Quality Act) requirements, and utility policies so your project stays on track.
Why Work With Soundproof San Diego?
We are an acoustics company with deep expertise in utility noise studies, residential and commercial noise control, and compliance-based acoustic assessments. Our focus is on accurate measurement, analysis, and reporting—ensuring that your project meets utility and municipal sound requirements without unnecessary delays.
Here’s why developers and engineers trust us:
Familiarity with SDG&E documentation and submission formats
Local experience with San Diego County zoning and enforcement
Ability to interface with project stakeholders and municipalities
Rapid turnaround for projects on tight timelines
Transparent communication and site-specific analysis
We deliver clarity, compliance, and professionalism—so your project can move forward with confidence.
Request a Transformer Sound Study Today
If SDG&E or your local utility has asked for a transformer sound study, don’t wait. These studies take time to schedule, measure, and document—especially on active construction sites.
At Soundproof San Diego, we provide fast, professional acoustic studies that meet all regulatory standards and help you keep your project on track.
Contact us today to request a proposal or schedule an initial site visit.
