We Turned a Bank Vault into an Audio Lab šŸ‘€ – Part 1

Here at Amplify Labs, we do quite a bit of audio design work for consumer electronics, medical, and industrial products that requires physical acoustic measurement space. We help quantify metrics like acoustic frequency response, THD (Total Harmonic Distortion), Rub and Buzz, Echo Loss, Double Talk Attenuation, and Noise to name a few. These metrics help tell us whether audio product features like voice commands and VoIP calls will work well for a user or will fall short of expectations; or whether the sound of a smart speaker will be pleasant, or shrill and unbalanced.

Sometimes a quiet room will suffice for these activities. Other times something more controlled is needed – like an anechoic or hemi-anechoic chamber.

We’ve had quite a challenge over the years trying to turn traditional office space and conference rooms into labs for acoustic measurement. Comfortable HVAC, beautiful floor to ceiling glass, polished concrete floors… these are all fantastic for most companies. Not for us. These office features account for increased noise and acoustic reflections which make measurements difficult and inconsistent. So as we began looking for a new space in the Bay Area, we were faced with some difficult choices for a small business in a large metropolitan area –

  1. Buy a pre-fabricated chamber or “quiet room” and assemble it inside of an office space. This can be expensive and not always reliable, as it is difficult to avoid coupling noise into the room from the floor and walls of the office itself.
  2. Get an office space “shell” to build a chamber into. Using the existing structure of an office would be great, but custom build outs can take a very long time and be even more expensive than the 1st option.
  3. Make due with traditional office space and conference rooms. This is the default, scrappy approach and we would be at the mercy of building construction and many other variables.

Starting out, the first and second options weren’t really viable. These approaches would require more time and resources than we could afford. So we went on a quest for traditional office space with a goal of finding a quiet place that we could be loud in. Sounds simple enough, but a year into it, we were still looking… Sky-scrappers were far enough away from low frequency road noise, but had too much glass. Flex/warehouse buildings didn’t have glass or anything fancy – sometimes not even bathrooms, but they were mostly around other loud businesses with heavy machinery.

While touring a sky-scraper in downtown San Jose, we noticed a stairwell going down from the first floor. Where on earth does that go?! Turns out a lot of older buildings in San Jose (renovated or not) have basements. We started asking around at each of the buildings we’d previously toured and most of these basements were just being used for storage. We were on to something.

We found a hidden gem near San Pedro Square in Downtown San Jose. An old bank building with a basement and bank vaults in tact. The Anglo California National Bank building.

Anglo California National Bank Building 1942 Vs. 2022

The space’s initial condition was “retro” and needed some TLC. A far cry from the modern office space aesthetic, but once we saw the bank vault in the basement, we were in love. A concrete shell isolated from all surrounding noise with a giant vault door. šŸ˜

This pretty well solved the isolation problem – finding a quiet place to be loud in. But, then we were faced with a reverberation challenge. Concrete and sheet metal can be very reverberant, which is problematic when trying to make accurate and repeatable acoustic measurements. But still, we were on the right path and just needed to find a good way to control reverberation time. Check out Part 2 of this post coming soon where we’ll describe our technical goals and specifications for The Vault and how we adapted this space to control reverberation and make it more audio measurement friendly.

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