PP210 - Mainstream and Self-Contained Classroom Acoustics for Deaf and Hard of Hearing/Hearing Impaired

Abstract:
Acoustic classroom conditions are paramount for speech understanding. More so, for those children who are deaf or hard of hearing or who have auditory processing disorders. ANSI standards recommend acoustic parameters such as, signal to noise ratio (SNR) and reverberation time RT60 be implemented into the architectural design. This study measured acoustic conditions in 20 “Mainstream” and 20 “Education of the Deaf and Hard of Hearing” classrooms. Findings revealed overall average reverberation times were adequate, but ambient noise levels and SNR were not within the ANSI standards.

Summary:
The detrimental effects of poor classroom acoustics have been studied over the past several decades. Poor acoustics have shown reduced and limited speech understanding ability for normal hearing and a greater reduction for those sensorineural hearing loss students (Crandell & Smaldino, 1995; Johnson, 2000; Lewis et al., 2016). Additionally, children with cochlear implants, auditory processing disorders in mainstream classrooms along with those who have central learning disabilities may also be at a disadvantage. (Wilson, et. al., 2011) (Inglehart, 2015). American National Standards Institute (ANSI) made formalized recommendations for acceptable acoustics conducive for an adequate learning environment (ANSI/ASA S12.60, 2010).

Acoustic measures were obtained on 40 unoccupied classrooms, 20 mainstream and 20 Education for the Deaf and Hard of Hearing (EDHH) “self-contained”. Classrooms were measured in a consistent manner for; classroom size (volume cubic feet), RT60 (reverberation time average of 500, 1000, and 2000 Hz), overall background noise in dBA (5 key locations taken from 10’ center of speaker, and 15’ and 20’ left and right of speaker.) and signal to noise ratios (SNR) (signal recorded speech at 60 dBA at 2 meters). Reference made if the Heating Ventilation Air Condition (HVAC) units were “off” or “on”.

Ambient noise in the Mainstream classrooms ranged from 29.6 to 46 dBA and 29.6 to 48.6 dBA in the EDHH classrooms. Statistical t-test revealed EDHH classrooms have greater noise levels than the When compared to ANSI/ASA S12.60 guidelines 12/20 (60%) of Mainstream classrooms, and 17/20 (85%) of EDHH classrooms, did not meet the 35 dBA criteria for rooms under 20,000 ft3.

Signals measured in the same strategic locations, ranged from 46.8 to 56.4 for the Mainstream classrooms and 48.8 to 54.3 dBA with for EDHH classrooms. Statistical analysis did not find a significant difference between the groups.

The SNR (subtracting the noise from the signal) for the Mainstream classrooms ranged from 6.2 to 19.2 dB and .7 to 23.1 dBA for the EDHH classrooms. Comparison of the SNR did not show a significant difference between the Mainstream and EDHH classrooms. Of the Mainstream classrooms 7/20 (35%), and 4/20 (20%) of the EDHH classrooms met the ANSI/ASA S12.60 guidelines.

Reverberation times (RT60) ranged from .195 to .956 seconds for Mainstream and .186 to .746 seconds for EDHH classrooms. For Mainstream, 3/20 (15%), and EDHH 1/20 EDHH (5%) classrooms, did not meet the recommended reverberation time of .6 seconds set forth by the ANSI/ASA S12.60 guidelines.

The ANSI/ASA S12.60 (2010) standards are not required but recommendations for architects/builders to improve classroom acoustics. Numerous factors must be considered are, budgetary constraints, size of the building/classrooms to accommodate large number of students and overall aesthetic design. These factors could interfere with and supersede newer acoustic designs. However, in retrospect, improvements have been made to modify the classroom interior by teachers and educators for the deaf and hard of hearing who are aware of problematic sound/hearing issues.