Sound+Off

SOUND OFF! An acoustical comparison of three Ball State University lecture halls.

Austin Pontius Department of Architecture Ball State University Muncie, IN 47306 aapontius@bsu.edu

Christopher Crosley Department of Architecture Ball State University Muncie, IN 47306 cjcrosley@bsu.edu


 * ABSTRACT: **

The materiality of a lecture hall plays a vital role in its acoustic quality and can often be changed or supplemented at a relatively low cost. Therefore, this study examines the acoustic quality of three lecture halls on campus based on qualitative feedback and analysis as a means to evaluate the acoustic effectiveness of the materials used in those spaces. By examining feedback we gained from an articulation test and qualitative evaluations of architectural acoustics we found that the different materials within a space affect the acoustic performance of the space. Then by observing the properties of these materials we concluded that the acoustic performance of the space depends more specifically on the materials' ability to absorb sound. This study proves that by adding or removing absorptive materials one can harm or improve the acoustic performance of a given space with relative ease.


 * INTRODUCTION:**

Professors' abilities to communicate with their students is one of the most important aspects of any education system, and the way it is being done is evolving every day. Thanks to technology professors are communicating in innovative ways that they never have before, ranging from immersive Internet activities, to video conferencing that can be done from halfway around the world. With such amazing strides in communication technology it is interesting therefore that so little has been done to improve the most basic form of communication that occurs on college campuses every day, which is lecturing.

It is likely that on almost any college campus, including Ball State’s, one will experience a lecture hall in which it is difficult to hear or understand the professor’s speech. This is often due to the poor acoustic quality of the space. One specific example of this problem is room number 217 located in the art museum (AR) on the North Quad of Ball State University’s campus. Professors commonly receive complaints from students about their ability to hear what is being said in this space. This is a problem because such an inability is threatening to a student’s performance within the space.

Because of the academic threats of poor acoustics we decided to conduct this study to better understand what affects the acoustic quality in a space. To determine this we decided to compare three different Ball State Lecture halls and analyze what makes them acoustically better or worse than the others based on their materiality. These lecture halls include, room AR 217, room 100 in the Architecture Building (AB), and room 175 in the Arts and Journalism (AJ), which are all similar in shape and size but differ mostly in their age and materiality. The ways in which we will compare these spaces will be by conducting an articulation test and a qualitative evaluation, which are based on previous techniques used to study acoustics such as the speech sample method used by the University of Berkeley in their Acoustic Study of Clear Speech[|(4)], and the methods and research in qualitative evaluation of architectural acoustics derived by assistant professor Ifan Payne of the University of Maryland[|(5)]. Since the rooms are similar in most ways besides materiality these tests will give us a reasonable idea of what materials enhance the acoustic quality of a space and which do not.

By completing our articulation test and qualitative evaluations we will be able to analyze which lecture hall has the best acoustics. We will then combine that knowledge with information on materials within the space to determine which materials have the highest value acoustically and draw conclusions on how to improve spaces with poor acoustic qualities through the use of these materials. Hopefully these solutions may then be looked toward as a reference on how to improve areas such as AR 217 and other educational facilities for the sake of improving the occupants’ performance within them.






 * HYPOTHESIS: **

The acoustic quality of a space depends on the abilities of its materials to absorb sound.


 * METHODOLOGY: **

To test our hypothesis, we will, with a small group of students conduct an articulation test, and a qualitative survey about the acoustic properties of the spaces. We will then rank the spaces in acoustic quality based on the statistics we gain. After we rank the spaces we will conduct a thorough investigation of the materials sound absorption properties.

__ EQUIPMENT: __

Articulation Test Qualitative Evaluation Survey Digital Camera

__ STEP ONE: Conduct Articulation Tests & Qualitative Evaluations: __

We will obtain qualitative data about each of the lecture halls by conducting an articulation test with a small group of 4 or 5 students to test their ability to hear a selected word set when placed around the room. Immediately after this test is conducted we will distribute an evaluation to learn how the participants perceived the acoustic quality of the space.

The articulation test will consist of 12 similar sounding words ( bait, bayed, bed, bet, bid, bit, paid, pat, ped, pet, pid, pit ) randomized and repeated for a total of 36 words, and will be conducted three times in each hall (front, middle, and back of the room). If the hall's acoustics are poor the participants will be unable to distinguish or identify the words. The qualitative evaluation will consist of a series of 1 to 10 ratings of various acoustic qualities. The lower the number the student selects the better the student perceives the space to be acoustically.

__Articulation Test Sample:__

bed, bayed, pet, bit, pid, bet, pat, bid, ped, bait, pit, paid, pid, bait, pat, bid, pet, bet, bed, pit, ped, bayed, paid, bit, pat, bait, ped, bed, bit, paid, bid, pet, pit, pid, bet, bayed.

__Qualitative Evaluation Sample:__

**Qualitative Evaluation of Architectural Acoustics**
 * //On a scale of 1 to 10, 1 being the best and 10 being the worst, how would you describe each of the following in the room?//**

The loudness of the direct sound: 1 2 3 4 5 6 7 8 9 10 good................ bad

The definition or clarity of sound: 1 2 3 4 5 6 7 8 9 10 good................ bad

The uniformity of sound in the space: 1 2 3 4 5 6 7 8 9 10 good............... bad

The amount of echo in the space: 1 2 3 4 5 6 7 8 9 10 good................ bad

The amount of noise, or negative sound in the space: 1 2 3 4 5 6 7 8 9 10 good.................bad

__ STEP TWO: Analyzing Data __

Using the data obtained in step one we will rank each space based on their acoustic quality. The percentage scores of the articulation tests of each of the participants will be averaged together to gain an articulation percentage result for each room. The results of the qualitative evaluations will be used in addition to support or negate the results of the articulation tests previously conducted.

__ STEP THREE: Material Investigation __ We will then document the materials used in the space by taking pictures of each of the walls, the ceiling, and the floor, and then analyze them focusing specifically on sound absorption and research how their qualities contribute to the acoustic quality in the space.

**DATA:**

__ARTICULATION TEST RESULTS:__ Note: The results for AB 100 were taken while both partitions where closed.
 * || AB 100 || AR 217 || AJ 175 ||
 * Student 1 || 83% || 60% || 75% ||
 * Student 2 || 86% || 63% || 72% ||
 * Student 3 || 78% || 54% || 66% ||
 * Student 4 || 66% || 39% || 51% ||
 * Student 5 || 66% || 42% || 48% ||
 * Totals || 76.4% || 51.6% || 62.4% ||

__QUALITATIVE EVALUATION RESULTS:__

AB 100: AJ 175: AR 217:
 * =  ||= Loudness ||= Clarity ||= Uniformity ||= Echo ||= Noise ||
 * = Student 1 ||= 3 ||= 3 ||= 4 ||= 4 ||= 3 ||
 * = Student 2 ||= 2 ||= 4 ||= 4 ||= 3 ||= 2 ||
 * = Student 3 ||= 4 ||= 4 ||= 3 ||= 2 ||= 3 ||
 * = Student 4 ||= 5 ||= 5 ||= 4 ||= 3 ||= 2 ||
 * = Student 5 ||= 2 ||= 2 ||= 2 ||= 3 ||= 3 ||
 * = Average ||= 3.2 ||= 3.6 ||= 3.4 ||= 3.4 ||= 2.6 ||
 * =  ||= Loudness ||= Clarity ||= Uniformity ||= Echo ||= Noise ||
 * = Student 1 ||= 4 ||= 5 ||= 2 ||= 1 ||= 1 ||
 * = Student 2 ||= 5 ||= 6 ||= 4 ||= 2 ||= 2 ||
 * = Student 3 ||= 6 ||= 6 ||= 3 ||= 2 ||= 2 ||
 * = Student 4 ||= 7 ||= 5 ||= 2 ||= 1 ||= 1 ||
 * = Student 5 ||= 3 ||= 4 ||= 2 ||= 2 ||= 2 ||
 * = Average ||= 5 ||= 5.2 ||= 2.6 ||= 1.6 ||= 1.6 ||
 * =  ||= Loudness ||= Clarity ||= Uniformity ||= Echo ||= Noise ||
 * = Student 1 ||= 5 ||= 6 ||= 6 ||= 7 ||= 5 ||
 * = Student 2 ||= 4 ||= 5 ||= 5 ||= 5 ||= 4 ||
 * = Student 3 ||= 6 ||= 6 ||= 4 ||= 6 ||= 5 ||
 * = Student 4 ||= 7 ||= 8 ||= 7 ||= 7 ||= 6 ||
 * = Student 5 ||= 5 ||= 5 ||= 4 ||= 5 ||= 5 ||
 * = Average ||= 5.4 ||= 6 ||= 5.2 ||= 6 ||= 5 ||

Qualitative Evaluation Averages:
 * =  ||= AB 100 ||= AR 217 ||= AJ 175 ||
 * Front || [[image:ab_100_3.jpg width="400" height="263"]] || [[image:ar_217_1.jpg width="400" height="263"]] || [[image:aj_175_3.jpg width="400" height="263"]] ||
 * Left || [[image:ab_100_2.jpg width="400" height="263"]] || [[image:ar_217_2.jpg width="400" height="263"]] || [[image:aj_175_1.jpg width="400" height="264"]] ||
 * Right || [[image:ab_100_4.jpg width="400" height="263"]] || [[image:ar_217_3.jpg width="400" height="263"]] || [[image:aj_175_2.jpg width="400" height="263"]] ||
 * Rear || [[image:ab_100_1.jpg width="400" height="263"]] || [[image:ar_217_4.jpg width="400" height="263"]] || [[image:aj_175_6.jpg width="400" height="263"]] ||
 * Floor || [[image:ab_100_5.jpg width="400" height="263"]] || [[image:ar_217_5.jpg width="400" height="263"]] || [[image:aj_175_5.jpg width="400" height="263"]] ||
 * Ceiling || [[image:ab_100_6.jpg width="400" height="263"]] || [[image:ar_217_6.jpg width="400" height="263"]] || [[image:aj_175_4.jpg width="400" height="263"]] ||

**ANALYSIS:**

AB 100: - AB 100 ranked the best, though not excellent, with 76% a on the articulation test. -AB 100 ranked the best in the qualitative evaluation survey. - Materials by surface (percentages) and their Noise Reduction Coefficient:
 * Side || Material || % of side || NRC ||
 * Front ||  ||   ||   ||
 * || Cast in place concrete || 25% || .05 ||
 * || Plywood 3/8" Paneling || 75% || .10 ||
 * ||  || Average: || **.0875** ||
 * Left ||  ||   ||   ||
 * || Cast in place concrete || 50% || .05 ||
 * || 3/4" Mineral fiber panels || 50% || .65 ||
 * ||  || Average: || **.35** ||
 * Right ||  ||   ||   ||
 * || Cast in place concrete || 40% || .05 ||
 * || 3/4" Mineral fiber panels || 50% || .65 ||
 * || Window glass || 10% || .15 ||
 * ||  || Average: || **.36** ||
 * Rear ||  ||   ||   ||
 * || 3/4" Mineral fiber panels || 35% || .65 ||
 * || Wood 1/4" paneling with airspace behind || 65% || .10 ||
 * ||  || Average: || **.293** ||
 * Floor ||  ||   ||   ||
 * || Wood flooring || 100% || .10 ||
 * ||  || Average: || **.10** ||
 * Ceiling ||  ||   ||   ||
 * || 3/4" Mineral fiber panels || 50% || .65 ||
 * || Concrete waffle slab || 50% || .05 ||
 * ||  || Average: || **.35** ||

AJ 175: - AJ 175 ranked the second best with a average total of 62.4% on the articulation test. -AJ 175 place second in the qualitative evaluation survey. - Materials by surface (percentages) and their Noise Reduction Coefficient:
 * Side || Material || % of side || NRC ||
 * Front ||  ||   ||   ||
 * || 5/8" Drywall || 65% || .05 ||
 * || Wood paneling || 35% || .10 ||
 * ||  || Average: || **.0675** ||
 * Right ||  ||   ||   ||
 * || 5/8" Drywall || 15% || .05 ||
 * || 3/4" Mineral fiber panel || 85% || .65 ||
 * ||  || Average: || **.56** ||
 * Left ||  ||   ||   ||
 * || 5/8" Drywall || 15% || .05 ||
 * || 3/4" Mineral fiber panel || 85% || .65 ||
 * ||  || Average: || **.56** ||
 * Rear ||  ||   ||   ||
 * || 3/4" Mineral fiber panel || 95% || .65 ||
 * || Window glass || 5% || .15 ||
 * ||  || Average: || **.625** ||
 * Floor ||  ||   ||   ||
 * || Heavy carpet on concrete || 100% || .29 ||
 * ||  || Average: || **.29** ||
 * Ceiling ||  ||   ||   ||
 * || 5/8" Drywall || 40% || .05 ||
 * || Acoustic ceiling tile, 3/4", suspended || 60% || .95 ||
 * ||  || Average: || **.59** ||

AR 217: -AR 217 ranked the worst on the articulation test by far with an average score of 51.6%. -AR 217 placed the worst in the qualitative evaluation survey. - Materials by surface (percentages) and their Noise Reduction Coefficient:
 * Side || Material || % of side || NRC ||
 * Front ||  ||   ||   ||
 * || Curtained stage || 60% || .50 ||
 * || Plaster || 20% || .05 ||
 * || Wood paneling || 20% || .10 ||
 * ||  || Average: || **.33** ||
 * Right ||  ||   ||   ||
 * || Window glass || 30% || .15 ||
 * || Plaster || 40% || .05 ||
 * || Wood paneling || 30% || .10 ||
 * ||  || Average: || **.095** ||
 * Left ||  ||   ||   ||
 * || Window glass || 30% || .15 ||
 * || Plaster || 40% || .05 ||
 * || Wood paneling || 30% || .10 ||
 * ||  || Average: || **.096** ||
 * Rear ||  ||   ||   ||
 * || Plaster || 60% || .05 ||
 * || Wood paneling || 40% || .10 ||
 * ||  || Average: || **.07** ||
 * Floor ||  ||   ||   ||
 * || Wood flooring || 100% || .10 ||
 * ||  || Average: || **.10** ||
 * Ceiling ||  ||   ||   ||
 * || Plaster ceiling tile || 100% || .05 ||
 * ||  || Average: || **.05** ||


 * CONCLUSION:**

Based on the comparison of the results of our articulation test and our analysis of the sound absorption of materials, our hypothesis is correct. The acoustic quality of a space depends on the abilities of its materials to absorb sound. AR 217 with very low sound absorbing materials scored very poorly on the test, while AB 100 with higher overall sound absorption scored much better. However, we found with room AJ 175 that excellent acoustic quality is not achieved by simply adding more sound absorption, as this room scored only marginally better than AR 217. Rather, excellent sound quality is achieved when a balance between an excessively live and an excessively dead space is achieved, and the abilities of the materials in a space to absorb the right amount of sound is essential in achieving that balance.


 * REFERENCES:**

Egan, M. David. //Architectural Acoustics//. New York: McGraw-Hill, 1988. Print.

Grondzik, Walter T., Alison G. Kwok, Benjamin Stein, and John S. Reynolds. //Mechanical and Electrical Equipment for Buildings.// Hoboken, NJ: Wiley, 2010. Print.

Haahr, Mads. //RANDOM.ORG - True Random Number Service//. The School of Computer Science and Statistics, Trinity College, Dublin, Ireland. 14 Nov. 2011. [|].

Ohala, John J. //Acoustic Study of Clear Speech: A Test of the Contrastive Hypothesis//. University of California, Berkeley. International Symposium on Prosody: Yokohama, Japan. 1994. [|]

Payne, Ifan. //New Methods and Research in Qualitative Evaluation of Architectural Acoustics//. Tech. no. 20742. Maryland: University of Maryland, 2010. Print.