Combined effects of acoustics and indoor air quality on calculation performance: a laboratory experiment and a lab-dilemma investigation

What the study found

Pupils solved arithmetic in a room held at 800 or 2000 ppm CO2 (pure CO2, between subjects) under five sound conditions: quiet, playground, birdsong and two ventilation-noise levels (47 to 52 dB(A)). CO2 had no effect on accuracy or speed, and there was no CO2 by sound interaction. Sound affected response time only, and only for mid noise-sensitivity pupils; lab responses were 0.9 to 1.6 s faster than in real classrooms and sounds ranked differently across the two settings.

Limitations

Pure CO2 without bioeffluents, and the authors estimate about 247 participants were needed to detect a CO2 effect. Lab sessions came months after classroom sessions, so order effects are possible.

Neurodesign interpretation

Adds to evidence that CO2 alone at 2000 ppm may not impair simple task performance, and warns that lab results on classroom acoustics may not transfer to real rooms.

Possible design implications

None yet. Keep ventilation targets; this argues for testing real under-ventilated air rather than pure CO2.

Study design

Laboratory experiment (split-plot) with lab-versus-classroom comparison

Population

Middle-school pupils, grades 7 and 8, mean age 12.8, Italy (neurodivergent and hearing-impaired pupils excluded). Sample: 165 analysed (189 enrolled); 118 in the lab-classroom comparison.

Setting

Two 96 m3 lab rooms furnished as classrooms, compared with the same pupils' real classrooms

Field

Indoor air quality, Acoustics + soundscape, Educational environments

Mechanism

Cognitive load, Working-memory interference

Spatial variable

CO2 concentration, Background noise level, Natural sound

Keywords

co2 concentration, background noise level, natural sound, cognitive load, working-memory interference

Notes and follow-up

Related records: ND-0003, ND-0004, ND-0005, ND-0025, ND-0026, ND-0023.