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The "Silent" Confound that Biomedical Research Ignores via

Science is filled with confounds; variables in our research that we don’t know about or don’t control. Confounds add a layer of variability and unpredictability to our studies, making it difficult or impossible to answer scientific questions. Good science is all about understanding the confounds in our work and systematically controlling or eliminating them from our studies, leaving our manipulation as the only remaining explanation for any changes we observe in our study.

That’s how it’s supposed to work. That’s how we’re all trained. Therefore, modern scientists work hard to control what’s in their animal’s diet, the light/dark cycles, we standardize their housing conditions and we even control their genetics. But unfortunately, we have largely ignored two of the greatest potential threats to our studies, noise and vibration. I consider these variables the “silent” confounds in biomedical research because they are present in every facility vivarium and lab, yet very few facilities and researchers measure them. As a result, they have no idea whether they are present or whether the variables might be impacting their work.

We have been into many research facilities to measure noise and vibration and every facility has a different noise and vibration profile. Indeed, just about every vivarium room within a facility has a different noise and vibration profile. So, it shouldn’t surprise us when a new investigator arrives at our facility and she can’t replicate her work.

Noise and vibration are not just interesting stimuli for hearing researchers like myself. They turn out to be especially optimal stimuli for rodents, a nocturnal species with a poor sense of vision, who have evolved to rely on their sense of hearing and touch/vibration to tell them what might be present by way of threats or mates or offspring in their dark tunnel environments. Indeed, noise and vibration are often used as model systems for studying stress in rodents. Unfortunately, there are two additional features that make noise and vibration especially problematic. First, we have increasingly brought mechanical and technical equipment into the vivarium and lab space near the animals. Whether it’s ventilated caging motors, cage changing stations, computers, or other technology, we are constantly introducing more noise and vibration into the vivarium and assuming that is helping our animals. Second, we have not had easy access to the equipment to measure these variables, especially for noise. Rodents hear ultrasonic sounds that we do not hear and many of our motors, lights, computers, and test equipment that we place around our animals generate ultrasonic noise that might be ear-piercing to our animals but not audible to us. Unfortunately, that means we can’t rely on our ears to hear what our animals hear and we need specialized equipment. Such equipment is more readily available now than it used to be.

If we know noise and vibration can serve as a confound for our research, and that the more equipment we bring into the vivarium the greater the risk, it becomes clear that our animals and our science can benefit from a better understanding of this silent confound. So, let’s start measuring!

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