PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Qualitative evaluation of a classroom redesign
Ana M. JARAMILLO1; Bruce C. OLSON1; Peggy NELSON2; Sarah BOCHAT2, Michael DOING212

AFMG Services North America, United States

Speech-Language-Hearing Sciences, University of Minnesota, United States

ABSTRACT
Shevlin Hall is home to the University of Minnesota’s Speech-Language-Hearing Sciences department.
Besides the typical needs of any educational space, some of the rooms have additional requirements to meetthe needs of a hearing-impaired population. In a previous study, we presented the results of a renovation ofclassroom 110 that addressed the room acoustics and electro-acoustics redesign, to achieve adequate speech
intelligibility. This study presents the results of a qualitative study of the impressions of the building users
before and after the renovation of classroom 110.
Keywords: Classroom, Speech, Intelligibility

1. INTRODUCTIONClassrooms are one of the environments with the highest need for good speech intelligibility. In
general, classrooms (re)designed during the last couple of decades in the United States, include anabsorptive ceiling, which provides an appropriate, if not necessarily ideal, acoustic environment.
However, classrooms continue to often use noisy mechanical systems and are rarely under the ambient
noise level recommended by the current ANSI 12.60 standard [1,3].
In a typical classroom there are 3 communication paths: Teacher to student, student to teac her andstudent to student. The third path is rarely considered. Communication between the students is thecause of incidental learning. This is critical especially for those with hearing impairment as it leaves
them out from the questioning and opinions of their peers. In order to reinforce all three paths ofcommunication, is important to first address the room acoustics, including reverberation time andambient noise. Secondly, a voice reinforcement system should be added where necessary.

2. SHEVLIN HALL RENOVATION
The department of Speech-Language-Hearing Sciences of the University of Minnesota is located ina historic building. Shevlin Hall has changed uses and finishes throughout the years, and in 2013, it
was necessary to undergo a renovation of classroom 110, formerly the main lounge of the building,
now often used as a multipurpose space for activities including classes, poster sessions and social
receptions.

1
2ana.jaramillo@amfg.eu, bruce.olson@afmg.eu
nelso477@umn.edu

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Figure 1. Shevlin Hall (before renovation)
The renovation included adding absorptive panels to meet the standard’s recommendation forreverberation time (0.8 s for a large classroom), and adding a new sound system to achieve goodspeech intelligibility. As the space is often occupied by people with a range of hearing deficiencies,
good speech intelligibility was critical for the functioning of the space.

Figure 2. Source and receiver locations for testing.
2.1 Ambient NoiseThe cooling of the classroom during the summer is done by 2 large window units. The update of thecooling system was not part of the renovation so the units continue to be functioning in the spaceresulting in a high ambient noise of NC56-62. Only one of the 2 units was operating during ourmeasurements.
2.2 Reverberation TimeThe room had a few absorptive panels but these were not enough for its use as a classroom and thehigh reverberation time made it hard to achieve good speech intelligibility.
With the addition of 35 absorptive panels, the reverberation time was brought down to the desired
range [4]. Figure 3 shows the RT measured at 3 locations in the room (see Figure 2) before (black) andafter (grey) the renovation. Optimal RT for a classroom of its size was achieved with the added
absorption.

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Figure 3. Measured RT at 3 locations

2.3 Speech Intelligibility
Speech Transmission Index was measured in the room at the same 3 locations and it showed valuesof 0.56-0.58 without the AC units running. With the lower RT and the new sound system, STIs of
0.68-0.76 were achieved.
The current standard recommends values above 0.64 for spaces that require very high speech
intelligibility, but 0.60 is considered acceptable [2].
In Figure 4 we see the results of STI measurements with (black) and without (grey) the soundsystem on, at locations across the room with the source at the instructor and back locations. The lightgrey baseline shows the highest level measured before the renovation, so we can appreciate theimprovement in STI given by the added absorption, and then the improvement given by the new soundsystem.

Figure 4. Measured STI with and without Sound System, after the renovation.

3. SUBJECT TESTINGIntelligibility subject-based tests were performed in the room, to compare with the speech
intelligibility predicted through STI. These tests were performed using IEEE sentences, played backthrough a single speaker at the front.
3.1 Speech Intelligibility
For speech played in quiet conditions, 4 tests were done using 3 receiver locations (instructor, frontand back) and 2 source locations (instructor and back).
Table 1 shows the results of this test.

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Table 1. Results of intelligibility test in quiet condition
Test
1Receiver Location

Source location

Results (Average %)Front

Instructor

78

2

BackInstructor

79

3

Front

Back804Instructor

Back68In quiet conditions, all subjects were able to get more than 68% of the spoken sentences. The pathfrom the instructor in the front corner to the receiver in the center back of the room was the poorest.
This condition would be highly improved by the use of the sound system.
The second test compared speech intelligibility in quiet and noisy conditions. For the noisycondition, the window AC units were running (~52 dBA).
Table 2 shows the results of this test.
Table 2. Results of intelligibility test in quiet vs noisy conditions
Test
1Condition

Receiver Location

Source location

Results (Average %)

Quiet

Front

Back94

Noisy
2

Quiet

6
Instructor

Back94Noisy

2

The comparison between noisy and quiet conditions is clear. The high noise levels make the room
unusable without the aid of the sound system.
3.2 Survey
In order to get a subjective impression of the users of the classroom, 2 open-ended questions weredistributed after a poster-session, inquiring about the ease of communication. During the session, there
were 4 posters being presented simultaneously.
How easy is it to understand the presenters?
Easy 6
OK 6

Difficult0

How easy is it to understand the poster discussion?
Easy 7
OK 5

Difficult0

The results from the survey show that it was fairly easy for people to understand an individual
poster presenter and discussion around it, even in the presence of distracting activity noise aroundthem. Additional survey results from long-standing faculty indicated great improvement in speech
understanding and vocal effort following the renovation. The achieved RT helps provide anenvironment in which this type of activity can be done successfully.

4. FINAL REMARKS
Shevlin Hall 110 started as a historic room with a high reverberation time and very high backgroundnoise levels where typical classroom activities could not be done. After the renovation of the room, thehistorical character was maintained but the reverberation time was lowered to the recommended levels.
An addition of an appropriate sound system completed the renovation to achieve very high spee chintelligibility. Even though the noisy AC units continue to exist in the room, it is only a small portionof the year where their use is required (due to its location in the colder Minnesota climate). Future
renovations of the building hope to address this need. Subject-based testing as well as an open-ended

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survey helped compare the predicted and measured room acoustics and the actual user experience ofthe room. All users found the room to be appropriate for its use as a classroom as well as otheractivities. Further investigations into the comparison between subject-based testing and speech
intelligibility predictions using STI are needed.

REFERENCES[1] American National Standards Institute. Standard 12.60-2010: Acoustical performance criteria,
design requirements, and guidelines for schools, Part 1: Permanent Schools. (2010)[2] International Electrotechnical Commission. Standard 60268-16, 4th Ed. Sound system equipment –Part 16: Objective rating of speech intelligibility by speech transmission index. (2011).
[3] Jaramillo AM, Ermann M. Noise in the classroom. Proceedings on Meetings on Acoustics. (2010).
[4] Olson BC, Jaramillo AM. Measurements for simulation of speech intelligibility in spaces withconflicting requirements. ICA 2016 Conference Proceedings. Buenos Aires.

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