Description of the space.  Foyer outside Seaver Auditorium, between Seaver North and Seaver South buildings, Pomona College.

Seaver Auditorium is host to many events in the natural science departments at Pomona College.  It holds large introductory science classes such as General Chemistry, Organic Chemistry, Introductory Physics, and others.  Visiting lecturers give their talks in the auditorium.  Accordingly, the foyer outside it is also full of people on a regular basis.  Whenever the large sections in the auditorium get out, the foyer is filled with students.  After an Organic Chemistry exam, students hang out in the foyer afterwards, nervously discussing what they wrote.  After a lecture from an esteemed visitor, groups of professors and students congregate in the foyer, chatting for long after the talk is over.

The foyer itself is not much to look at.  It is a utilitarian 30 ft cube with one open face pointed towards College Avenue, a major thru street (see diagram below).  It is made entirely of grey concrete, with no ornamentation except for the back wall, where the doors to the auditorium are.  This wall has vertical grooves spaced 2-3 inches apart.  I wonder if this is to help with reverberation, since the space is entirely concrete.  Four square pillars are evenly spaced in the center.  The floor is made of dull reddish brown tile. The metal double doors to the auditorium are dented from wear.

Recording setup. I popped the balloon about 5 feet in front of the doors to the auditorium.  The microphone was located about 10 feet away, sitting on a concrete bench, about 2 feet from the concrete wall (see diagram below).

Reverberation time.

30 dB decay: 0.64 sec

50 dB decay: 1.42 sec

60 dB decay: 2.35 sec

Decay to background level: 2.92 sec

Acoustic Description.  The foyer readily amplifies and echoes sound—the microphone was at least 10 feet away and still picked up a maximum decibel level of 85 dB.  This is due to all the hard surfaces present, as there is nothing but concrete walls, concrete ceiling, concrete floor, and metal doors.  The balloon pop had a relatively long decay time: it took 2.9 sec to return to the background noise level.

The foyer has significant background noise, since it readily amplifies passing cars on College Ave, which is about 50 feet from the opening.  This can be seen in the spectrogram:  there is noticeable volume in the 20 to 200 Hz range before the balloon pop.  These frequencies are intensified with the balloon pop, but after the higher frequencies associated with the balloon pop have decayed, this background noise is still present.  This suggests that the foyer is adept for echoing sounds in this lower range.