Noise levels in the B201 classroom used in algebra and trigonometry

In 2002 the American National Standards Institute (ANSI) created ANSI S12.60-2002, an Acoustical Performance Criteria, Design Requirements and Guidelines for Schools standard. "...In 2004, the American Speech-Language-Hearing Association's (ASHA's) Working Group on Classroom Acoustics recommended that an appropriate acoustical environment be established in all classrooms and learning spaces. ASHA endorses the ANSI standard and recommends the following criteria for classroom acoustics:

  • Unoccupied classroom levels must not exceed 35 dBA 
  • The signal-to-noise ratio (the difference between the teacher's voice and the background noise) should be at least +15 dB at the child's ears. 
  • Unoccupied classroom reverberation must not surpass 0.6 seconds in smaller classrooms or 0.7 seconds in larger rooms" 

World Health Organization acoustic standards also recommend that "background sound levels should not exceed 35 dB LAeq." These guidelines are often reflect in European Union member nations noise guidelines for classroom.

Classroom noise is known to have strong negative impacts on learning and student performance.

Background noise levels above 60 dBA are rated as being uncomfortable for learners and unacceptable in a classroom. As teachers have to speak at 15 to 20 dBA above the background noise, teachers must raise their own voice to 75 to 80 dBa, a very high and exhausting volume. I

In general all of the college classrooms are, relatively speaking, noisy. The rooms with air conditioning have significant air conditioning noise along with the noise of the technology in the room. The non-air conditioned rooms typically have cement floors and ceilings which make for extremely poor sound absorption and high levels of sound reverberation. These rooms have fans which vary in age and condition, many of which produce a variety of repetitive sounds.

Fan in B201 classroom

A sound analyzer app was used to gather sound level data using the most often recommended A-weighted sound profile for a equivalent continuous sound level. Data was gathered in a number of environments. This data was gathered using a smartphone and cannot be considered more than an indication of potential noise issues. The actual values obtained with professional acoustic equipment properly calibrated will likely differ. In general, however, the measurements provide a first look at the noise levels in selected classrooms at the college.

While both ANSI and WHO recommend background noise levels of 35 dBA in the classroom, this is clearly difficult to achieve in the college classrooms. For now the goal might be to get background noise levels below those which are proven to negatively impact learning, those classroom with sound levels above 60 dBa.

The background sound levels in the A204 mathematics and science computer laboratory were measured early in the morning before class. At this time only the air conditioning units running along with the SMARTboard and a network hub (fan noise) were running. The room produced a reading of 42 dBA.

For reference purposes, the mathematics and science division office at midday produces a background noise of 50 dBA. There air conditioning and printers contribute to the background noise.

The physical science classroom, A101, has steel chairs that have lost their plastic "boots." As the students enter and slide the chairs on the tile floor, these chairs produce sound levels of 76 dBA at a distance of there meters. Noting that sound measurements are typically to be done at a distance of one meter, the noise level of the chairs sliding on the tiles would be louder at that reference distance. ​Once the class has settled into their chairs, the physical science classroom produces about 60 dBA of background sound. The background sound is a combination of fan noise, external noise, and the presence of 28 students in the room. Even as they sit relatively quietly, they produce some noise.

While relatively noisy, the nature of the sound in the A204 classroom is perceptually less disruptive to the class.

The B201 mathematics classroom is a cement room with a cement ceiling and walls. Louvered windows open on either side of the room.

B201 classroom

The sound level at the front teacher's desk is 62 dBA, an uncomfortably loud noise level. Directly under the noisiest fan the noise rises to 63.4 dBA. The bulk of the background noise in B201 is the fans. If the fans are turned off, the room becomes quite warm as the air stagnates (unless a stiff breeze happens to be blowing at an optimal angle). The class meets at 2:10 PM, in the heat of the afternoon. The hot room conditions would also negatively impact learning. The nature of the sound is also perceptually high impact: repetitive clinkings, clankings, and clickings.

Even if the students were first language English learners, this level of noise would be unacceptable. Given that the students are working in English as a second language, the learning situation is untenable.

As an end note, one of the classes in B201 is an experimental algebra and trigonometry class. This is the first time in 20 years that an algebra and trigonometry class has been held outside of the computer laboratory. The class is using online resources, a new WiFi antenna, and student's own personal technology devices as integral parts of the curriculum. This is a one-off experiment to see whether algebra and trigonometry can be taught outside of a computer laboratory using student supplied technology. Thus far the students are finding the class particularly challenging, perhaps the technological approach is simply a bridge too far for the students at this time. I cannot, however, rule out the detrimental impact of the noise environment in the classroom. B201 is significantly noisier than A204 - where the other algebra and trigonometry classes are taught, thus any learning difference might be due to environmental noise impacts.


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