Michael Ermann

Coupled Volumes: Aperture Size and the Double-Sloped Decay of Concert Halls

The coupled-volume concert hall and its signature double-sloped sound decay attempt to reconcile the often-competing qualities of clarity and reverberance. By wrapping a room with another more reverberant room, and allowing for apertures to control the sonic transparency between the two rooms, designers use coupling to provide a sound field that is variable, longer, distinct, and performance-piece-specific. For this study a coupled-volume concert hall (based on an existing hall) is conceived with a fixed geometric volume, form, and materiality. Aperture size is established as variable. The simulated hall undergoes statistical and geometric (ray tracing software) analysis. Results show disparity in the absolute decay patterns projected by the two methods; however, both statistical and geometric relative analyses suggest a highly sensitive relationship between the aperture size exposing the coupled-volume and the double-sloped condition. To test the model, simulations are compared to real-room measurements taken in a coupled volume concert hall.

Double Sloped Decay: Subjective Listening Test to Determine Perceptibility and Preference:

Can music listeners, both experienced and inexperienced, distinguish a double-sloped decay from a Sabine decay? Do they prefer the double slope? A simulated space, based on an actual built coupled-volume hall, was conceived in room acoustics software to create double sloped and classic Sabine auralizations. The simulated decays were compared with in situ measurements taken in a built coupled volume concert hall for validation. The impulse responses generated were convolved with an anechoic musical recording, grouped in pairs, and played for subjects. Participants listened to the recorded pairs over headphones and were asked to determine (1) if the two recordings sounded different, (2) which recording was more likely to have a double slope or had a more dramatic double slope, and (3) which of the two recordings they prefer. The more a recording diverged from a standard Sabine decay, the more likely the respondents were to identify that recording as having a double slope. When asked to identify a preference, subjects were no more likely to select a recording with a double-sloped decay, than a Sabine decay.

Pilot study: Exposure and materiality of the secondary room and its impact in the impulse response of coupled‐volume concert halls

What does one room sound like when it is partially exposed to another (acoustically coupled)? More specifically, this research aims to quantify how operational and design decisions impact aural impressions in the design of concert halls with acoustical coupling. By adding a second room to a concert hall, and designing doors to control the sonic transparency between the two rooms, designers can create a new, coupled acoustic. Concert halls use coupling to achieve a variable, longer, and distinct reverberant quality for their musicians and listeners. For this study, a coupled‐volume shoebox concert hall was conceived with a fixed geometric volume, form, and primary‐room sound absorption. Aperture size and secondary‐room sound‐absorption levels were established as variables. Statistical analysis of sound decay in this simulated hall suggests a highly sensitive relationship between the double‐sloped condition and (1) Architectural composition, as defined by the aperture size exposing the chamber and (2) Mater...

Classroom acoustics III: Acoustical model studies of elementary school classrooms

A 1:4 scale model was constructed with a series of interchangeable wall and ceiling panels to allow a battery of acoustical tests to be conducted for a variety of classroom designs. The walls and ceiling of the room could be changed from sound absorbent to sound reflective materials quickly. Scale furniture was also constructed for the room. The walls of the model could be adjusted from approximately 7 to 10 meters in length and from 2.5 m in height to 7 m in height. Acoustical measurements of speech transmission index, reverberation time, early reverberation time, early‐to‐late energy ratios, loudness (or relative strength), and articulation index were made in a number of simulated elementary school classrooms using both a TEF analyzer and impulse spark techniques. Classrooms where field measurements were taken as described in Classroom Acoustics II were modified to attempt to improve acoustical conditions in the rooms. The location and amount of absorbent material, the location and amount of sound refle...

Coupled Volumes: Secondary Room Reverberance and the Double-Sloped Decay of Concert Halls

The coupled volume concert hall and its signature double sloped sound decay aim to partially reconcile the often-competing qualities of clarity and reverberance. A concert hall is conceived with a fixed geometric volume, form, and aperture size. A coupled volume is attached and its materiality is established as variable. Both statistical and geometric relative analyses suggest a highly sensitive relationship between the coupled volume reverberation time and the double-sloped condition.

Coupled volume/double slope subjective listening test

Can experienced listeners of music discern a double‐sloped decay from a Sabine decay? Do they prefer the double slope? Concert hall designers use coupled‐volumes and their signature double‐slope sound decay in an effort to reconcile the inversely related qualities of reverberance and clarity. A simulated space, based on an actual built coupled‐volume hall, was conceived in the room acoustics software CATT‐Acoustic. Variations in the aperture sizes that sonically expose the main hall to the coupled volume generated both classic Sabine decays and double‐sloped decays. The impulse responses generated were convolved with the same anechoic musical recording, grouped in pairs, and played for an opportunity‐sample of 21 volunteers from the Architectural Acoustics section of the 145th meeting of the Acoustical Society of America in Nashville. Participants listened to the 11 recorded pairs over headphones and were asked to determine (1) if the two recordings sounded different, (2) which recording was more likely t...

Classroom acoustics I: The acoustical learning environment: Participatory action research in classrooms

This pilot study used participatory fieldwork in a number of kindergarten through eighth grade classrooms to evaluate the acoustic setting that supports learning. Dynamic interactions among administrators, teachers, students, parents, and research team members makes a difference in learning. It was found that classroom interaction depends on the social make‐up, anticipated behavior, intellectual level, teaching method and theories, and hearing capacity of participants, as well as the physical characteristics of the classrooms. Participatory action research (PAR) resulted in the development of appropriate classroom observation tools utilizing checklists, summary scales, and hierarchial rating scales. The learning climate, lesson clarity, instructional variety, task orientation, and student engagement were used to identify variables for acoustical studies. The PAR was instrumental in determining the protocol for the acoustical measurement studies described in Classroom Acoustics II. Field observations began...

Classroom acoustics II: Acoustical conditions in elementary school classrooms

Acoustical measurements of speech transmission index, reverberation time, early reverberation time, early‐to‐late energy ratios, loudness (or relative strength), articulation index, background noise levels, and signal‐to‐noise ratios were made in a number of elementary school classrooms in one school district to see how many rooms actually had acceptable acoustical conditions. The source and receiver locations for the acoustical measurements were determined through the participatory action research (PAR) described in Classroom Acoustics I. Measurements were made using a TEF analyzer with custom software to compute additional acoustical measurements. Both omni‐directional and directional loudspeakers were used for the source signals. The acoustical measurements were conducted in a variety of source receiver conditions as observed in the PAR studies in the classrooms. General observations are related regarding the relationship between the measurements and the PAR. For example, the STI was always greater tha...

Mapping speech transmission index (STI) and background noise in university classrooms

Noise and intelligibility measurements were taken in dozens of classrooms at approximately every-meter resolution and are presented as heat maps. In doing so we hope to determine (1) the largest (and loudest) classrooms that do not require loudspeaker speech amplification and (2) the radius of muddled intelligibility circumscribed around noise sources such as air diffusers and fan coil units.

Subjective listening tests: Perception and preference of simulated sound fields

Concert hall sound fields were simulated by architecture students and anechoic recordings were convolved to create auralizations in those simulated performance spaces. Then an architectural feature was altered digitally and a second track was auralized. College music students were recruited, tested for hearing loss, and brought to a low-reverberance room with a spatial sound array of 28 mounted speakers. They were asked to identify which of the two simulated tracks they prefer. We compared simulated performance spaces: (1) with four tiers of balconies vs with one tier of balcony; (2) with an over-stage canopy vs without a canopy; (3) with separate balcony boxes vs with a continuous balcony not fragmented by box walls; and (4) with a higher scattering coefficient vs a lower scattering coefficient. Those in the audience will be invited to judge preference between the tracks for themselves. The study will be framed by the extraordinary career arc of Bert Kinzey who engaged architecture students in the study ...