“Don't fix the fumes but compromise the learning”: Response to the letter by Matthew J. Zdilla: “Sound off: Noise in the gross-anatomy laboratory”

Dear Professor Organ,

We are grateful to Dr. Zdilla for addressing two inseparable challenges that face every contemporary dissection laboratory: first, protecting anatomy staff and students from formaldehyde or other volatile organic compounds, and second, achieving this without turning a place of learning into an acoustically stressful environment. Air-quality engineering has advanced steadily in recent years. However, noise control appears to remain an underappreciated determinant of both occupational safety and educational quality. Our remarks therefore will concentrate on the latter aspect.

Dr. Zdilla reports that his upgraded extraction system produces 69.2 dB(A) when operating, while the room background with the fans off is 38.6 dB(A).^{1, 2} These figures are highly valuable in their transparency. But they stand well above the targets that most European and North American guidelines set for spaces in which focused cognitive work takes place. Of note, the contribution of the 38.6-dB(A) source is most likely negligible for the entire setup presented. In reference to Dr. Zdilla's letter, in Austria, Guideline 5 of the Institute for Building Technology limits rooms devoted to concentrated tasks to 30 dB(A).³ The German DIN 18041⁴/VDI 2081⁵ and the World Health Organization's European Environmental Noise Guidelines⁶ recommend roughly the same for teaching rooms. The ANSI/ASA S12.60 applies a 35-dB(A) ceiling to US classrooms of ordinary size.⁷ The ISO 9921⁸ advises that background noise should remain below 45 dB(A) simply to preserve speech intelligibility. To put the gap in perspective, 69.2 dB(A) delivers about 15 times the perceived loudness—and roughly 8000 times the sound energy—than the 30 dB(A) reference. Above 80 dB(A), EU law obliges employers to offer hearing protection, and at 85 dB(A) its use becomes mandatory.

For the example outlined by Dr. Zdilla, the nominal limits still describe an unoccupied room. As soon as teaching begins, sound-pressure levels add logarithmically. Twenty-nine table groups (in our case)⁹ conversing at an ordinary 60 dB(A) apiece would raise the sound field in a 38.6 dB(A)^{1, 2} space to about 74.6 dB(A). Replacing the benign background noise with the 69.2-dB(A) fan noise reported by Dr. Zdilla pushes the total to roughly 75.7 dB(A). If each table were to be fitted with its own unit at 69.2 dB(A), the arithmetic approaches 84.3 dB(A)—narrowly below the legal threshold at which hearing protection must be worn. One might hope to recover a few decibels with the generous use of ceiling absorbers, wall panels or baffles. Yet, the physics of rooms limits such treatments to gains of perhaps 10 dB once a source exceeds 65 dB(A). In practice, therefore, bringing a 69.2-dB(A) extraction system down to the 50 dB(A) generally considered acceptable for laboratory spaces (and still well above the 30–35-dB(A) target, e.g., for examinations) is unattainable by acoustical finishes alone. Source-side measures—low-noise or variable-speed fans, duct silencers, vibration breaks and demand-controlled ventilation—would become essential at a high cost of installation. As outlined by Dr. Zdilla in his letter, a reduction in air exchange rates may form another measure to lower the sound emission profile, and at the same time to enhance user comfort and energy consumption in the sense of sustainable use.

From the pedagogical perspective, the stakes are high. Gross-anatomy sessions demand intelligible speech, sustained concentration, and precise manual work. A series of studies and meta-analyses demonstrate measurable declines in vigilance and learning once continuous background levels rise into the 40–50 dB(A) range.^10-12 Thus, an extraction design that removes chemical hazards at the cost of a steady ~70 dB(A) threatens to exchange one health risk for another. It may be argued that ordinary day-to-day dissection rarely satisfies “silent-room” ideals; nonetheless, formal spot tests, oral examinations, and flag practicals undeniably should, and can, be conducted within the 30–35 dB(A) band demanded of any other examination venue.

We therefore concur with Dr. Zdilla's assertion that “effective measures have to be taken,” but we add the caution that the acoustic footprint of any ventilation upgrade deserves the same evidentiary scrutiny as its toxicological benefit. A system that presently emits 69 dB(A) should not be seen as an end state but as a waypoint on the road toward quieter, source-controlled solutions. We hope these comparisons place the impressive engineering effort of Zdilla and colleagues in context and stimulate deeper collaboration between anatomists, occupational hygienists and building-acoustics specialists so that future laboratories can be at once clean, safe and truly conducive to learning.

Jürgen Russ: Conceptualization; methodology; data curation; validation; formal analysis; writing – review and editing. Niels Hammer: Conceptualization; methodology; writing – original draft; writing – review and editing; project administration; formal analysis; validation; data curation.