Facilities (Campus Spaces)

Active Learning and Case Study Classrooms

Classroom acoustics and audiovisual design


Some years ago, an architect friend and past client called with an issue: He had designed a new graduate school classroom, and there were some acoustical problems. It was a large, flat-floor room for up to 125 students, with moveable tables and chairs. The teaching model, called “active learning” or “teambased learning,” incorporated several classroom modes into each class session. The instructor first addressed the class and introduced a study problem. Students then worked through the problem in groups of six to eight, with each group sitting around its own table. Video displays mounted on walls around the room presented relevant facts about the study problem. After a set time had elapsed, each group presented its solution orally to the class.

In concept, this model is no different than what primary and secondary schools have practiced for generations. But adapting this familiar teaching model to a large classroom of 125 students rather than 30, with work groups of six or eight rather than three or four, proved challenging. Amplification was required for one person to speak and be heard by the entire room. In this room, microphones and loudspeakers were located in the ceiling, and a “mix-minus” signal-processing algorithm was intended to activate only the microphone closest to the person speaking and deactivate the loudspeakers closest to that microphone. The system was easily overwhelmed during group-work mode as up to 20 separate groups around the room talked and sometimes argued through their study problems, often quite enthusiastically. Overall sound levels in the classroom during these times could get quite loud, making discussions difficult. Additionally, the moveable furniture meant that microphones were not always located directly above student tables and did not always amplify speech effectively. Students were often asked to speak up and repeat themselves when presenting their groups’ solutions.

acoustics and audiovisual design


What went wrong with this design, and what can we do to get it right in other classrooms? Let’s take a step back and look at several traditional classroom models and their acoustical designs.

From Traditional to Today

Traditional primary and secondary school classrooms for 20 to 30 students accommodate a variety of teaching modes: instructor speaking to the class, full-class question/answer and discussion, individual teacher-student interaction and student group work. To control buildup of noise when many students are talking, and to promote clarity and intelligibility of speech, sound-absorbing ceilings are typically included in all such classrooms and are required by relevant classroom design standards, such as LEED, CHPS and ANSI S12.60. Because of the typical classroom size speaking distances are small, and amplification is not required.

acoustics and audiovisual design


ARE YOU GOING SOFT ON ME? A classic university lecture hall, such as the one seen to the left, was designed with hard surfaces that reflected an instructor’s voice to students’ ears. But reflection of sound adds reverberation, which adds distortion and can result in unintelligibility. Today’s lecture halls, such as the one above, are being designed with softer, sound-absorbing surfaces and furnishings, reducing reverberation and echoes. The science of sound has led designers to techniques and materials, as well as technologies, which create an optimal acoustical lecture environment that provide crisp and intelligible sound throughout the room.

Lecture and assembly halls are designed for one instructor or presenter to address a large number of students or audience members. Before the arrival of speech amplification, this required big voices and clear diction. Design of such rooms often included hard surfaces to reflect the instructor’s voice to the students’ ears, naturally reinforcing the speech while adding reverberation that challenges intelligibility. This design approach still applies today for performing arts theaters and other rooms intended for unamplified speech to large audiences. However, modern collegiate lecture halls are typically designed for amplified speech, and should be equipped with a properly designed sound system and sound-absorbing surfaces to promote clarity and intelligibility of that amplified speech.

Many collegiate lecture rooms of up to around 125 seats in size are used for what is sometimes called “case study” learning, which is a mix of lecture and seminar modes. The instructor will often be amplified and will lead a discussion among the class, while students are speaking unamplified. Allowing students to hear one another from any location in the room requires several design features:

  • Very low background noise from HVAC and other equipment,
  • sound-reflecting ceiling surfaces in the front and center of the room, and
  • sound-absorbing wall surfaces at the sides and rear of the room.

The combination and locations of sound-reflecting and sound-absorbing surfaces allow students’ voices to be naturally reinforced across the room, while at the same time controlling reverberation that could impede clarity and intelligibility. Equally important is the layout and furniture configuration. To keep speaking distances as close as possible, seating is typically fixed and dense, and the floor is often tiered to allow clear and direct lines of sight and sound among students.

acoustics and audiovisual design


HEAR AND BE HEARD. In Cornell University Law School’s Hughes Hall and Myron Taylor Hall, lecture halls are designed to include three projectors and projection screens as well as two large confidence monitors to allow the presenter to see what is displayed on the screens without having to turn around. The lecture halls are also equipped with sophisticated audio systems, including both microphones on the student desks and suspending from the ceiling, in order to support speech reinforcement and distance learning. Furthermore, videoconference codecs for distance learning and class capture appliances were installed to enable recording and storing classes for later review by students.

Accommodating Active Learning

The active learning model, with its flexible furniture layout, larger floor plan area per student and multiple speech and discussion modes, requires a very different design approach than these traditional models. Speaking distances are often too far to realistically allow for unamplified speech across the room, particularly when other students may be carrying on sidebar conversations with members of their group. In group-working mode, with its multiple simultaneous discussions at many tables, the room behaves acoustically more like a cafeteria than a classroom, and sound-absorbing material at the entire ceiling is needed to control buildup of activity noise. A speech-reinforcement system must be thoughtfully designed to allow amplification of only the intended speaker. Often, the best approach is to include push-to-talk tabletop microphones. If the furniture positions are fixed, ceiling heights are within reason and background noise is properly controlled, ceiling microphones may also be an option. In either case, a distributed ceiling loudspeaker system and mix-minus signal-processing algorithm are generally appropriate. To support flexibility, microphones may be connected to Ethernet ports and audio-distributed by the data network, avoiding the need for dedicated audio cabling.

Today’s college and university classrooms are innovating in many ways, combining and extending teaching methods that challenge our design practices. More than ever, designers must work to understand in detail how these rooms will be used so that our designs respond appropriately, and so that instructors and students can hear and understand one another clearly and easily.


Relative to audio engineering, a mix-minus is a particular setup, such that the output to a certain device contains everything except the input from that device. Mix-minus, which is technically accomplished via a wiring and patching configuration, prevents echoes or feedback from reverberating or howling and squealing through the broadcast or sound reinforcement system. A mix-minus signal is sometimes also known as a “clean feed” or a “Select Audio Return (SAR).”

A common example is in the field of sound reinforcement. Consider a room with sound stations for multiple users, each station containing a microphone and a loudspeaker. The microphone in station #1 would feed the loudspeakers in every other station except station #1. In other words, station #1 receives a mix of all microphones minus the station #1 microphone. This enables all participants to hear each other clearly but minimizes problems with acoustic feedback.

This article originally appeared in the issue of .