Acoustic assessment of four music rehearsal rooms in accordance with ISO23591 standard

Optimizing rehearsal room acoustics is crucial for musicians to perceive sound, pitch, and frequency variations. Since the introduction of the international standard ISO 23591 Acoustic quality criteria for music rehearsal rooms and spaces, research in the field of music rehearsal rooms has significantly intensified. However, relatively few have adopted an approach that integrates both objective measurements and subjective user evaluations, particularly in rehearsal rooms for quiet-category instruments. Therefore, this study aimed to assess and improve the acoustical conditions of four Turkish rehearsal rooms for quiet-category instruments using measurements, simulations, and musician surveys. A survey conducted in the first phase revealed that musicians rated the efficiency, satisfaction, and frequency balance of four rehearsal rooms as bad to fair. Efficiency of rehearsals showed a strong correlation with frequency balance (R² = 0.72 for low-to-mid; R² = 0.76 for high-to-mid). Strong correlations (R² = 0.93) were found between calculated and perceived low-to-mid frequency balance, while high-to-mid frequency balance showed weaker correlations (R² = 0.36), suggesting possible sensitivity to low-frequency issues; though this did not consistently align with user satisfaction, indicating that additional perceptual factors play a role. Acoustic measurements show that existing reverberation time (RT_mid) values for all rooms fall outside recommended limits. The measured rehearsal rooms were modeled, calibrated, and 36 acoustic models were developed with three alternative designs to improve acoustics within recommended limits. Then musicians from these rooms assessed 36 acoustic models through listening tests based on auralizations. Listening tests showed a preference for models with RT_mid values within the recommended range, aligning subjective and objective assessments. After the RT_mid value, effect of low-to-mid frequency balance was important in the choice of rooms for musicians.