Klaus Kleinschmidt

Cooperating with Miguel on improvements of the acoustical product - SOUNDBLOX

Some 15 years after joining Miguels consulting firm Cambridge Acoustical Associates around 1960 he asked me to help him with improving the sound absorbing quality of a patented slotted concrete block. The original concept of the block, sold under the trademark, SOUNDBLOX, was create a Helmholtz resonator by providing a slot in one face of a standard concrete block whose natural frequency would match the fundamental frequency of a common noise source, transformer hum. A broader absorption spectrum was desired to expand the rather limited applications of the original design to compete with acoustical materials widely used in schools, gymnasiums, auditoriums, and swimming pools. This presentation will describe the nature of our cooperation and the successes and failures of various concepts. The fact that the product, first introduced in the late 1950s is still on the market, reflects well on our collaboration.

Fire safety of acoustical materials

Recent deadly fires in overcrowded nightclubs used open cell foam material for sound absorption. The rapid progression of fire and release of opaque smoke contributed to the inability of some of the patrons to escape the fire. Suggestions for limiting the use of such materials in places of assembly are provided. Illogical use of such sound‐absorbing materials to reduce sound transmission to adjoining spaces or outdoors are discussed.

Real world issues in classroom acoustics for hearing impaired students

Experience is being gained from evaluating and modifying the acoustical properties and background noise levels of existing classrooms for use by hearing impaired students. Projects include more than 25 schools in public school systems that are mainstreaming handicapped children. Various practical and economic restrictions have led to recommendations for modifications that do not necessarily comply with ANSI S12.60 2002. Examples of real world conditions and practical solutions will be described.

A practical side of M. C. Junger

This is a chapter in the life of a man whose mind is in part filled with a mist of symbols and equations but which has another part that can create very practical applications of theoretical acoustics. I am fortunate enough to have shared for many years in Miguel’s prodigious intellectual output as well as his kindness and generosity. I will summarize the story of how he invented a product, basically made of dirt, about 50 years ago and of his participation in creating a unique and commercially successful acoustical material called SOUNDBLOX.

Representative noise levels of snow making, slope grooming, and other ski area equipment

In the process of producing the environmental noise assessment for a major expansion of the Mt. Wachusett (MA) ski area, noise data for ski area equipment were collected. Modern ski areas are highly mechanized. Snow making equipment includes large air compressors and snow guns or other air/water dispersal devices. Slopes and trails are groomed by special tractors towing various rollers, plows, scrapers, etc. to provide well‐packed mogul‐free surfaces. Much of the snow making and grooming activities take place at night. By day snowmobiles are used to transport the ski patrol to serious accidents and mechanics to repair stalled lifts. Construction of new ski trails requires additional, typically loud equipment such as chain saws, log skidders, wood chippers, bulldozers, etc. In the rural environment of ski areas these activities can exceed ambient noise at considerable distances. Furthermore, the trend to overnight accommodations for skiers directly on ski hills requires consideration of such equipment noise.

Acoustical characteristics of partitioned spaces under a modular grid of vertical sound absorptive surfaces

A facility requiting great flexibility in the size and arrangement of partitioned spaces for evaluating various computer systems was designed with fixed lighting and air conditioning diffusers. Sound absorption is provided by a 5‐ft (1.5 m) by 5‐ft grid of vertical acoustical panels consisting of fibrous glass and perforated metal facing approximately 15 in. (0.38 m) high and 2 in. thick. Measured room to room noise attenuation and the effective ceiling sound absorption coefficient compare favorably with a conventional continuous horizontal acoustical ceiling and partial partitions which extend to 2 to 3 ft below the ceiling. The open grid system eliminates the need to change the duct and diffuser layout and permits unrestricted access to the open plenum space for modifications of services and maintenance. Fire protection systems can also be hidden from view in the darkly painted plenum. The room to room noise reduction values of such an open grid system can be predicted by a simple model.

Noise control considerations in the modernization of a Boston subway station

The primary concern in the modernization program for the Park Street subway station was the intense wheel squeal on the sharply curved tracks (radii as small as 45 ft) at one end of the upper platform. Secondary concerns are reduction of the exposure of patrons to rolling and braking noise on the upper and lower levels. Measurements of existing acoustical conditions and typical noise levels of trains are described. The noise control treatments presently being installed and the anticipated reductions will be discussed. The practical performance characteristics required of acoustical materials for subway stations will also be summarized.

Comments on ’’Ambient noise level above plane with continuous distribution of random sources’’ [L. C. Sutherland, J. Acoust. Soc. Am. 57, 1540–1542 (1975)]

Data on the vertical gradient of noise levels outside high‐rise buildings in urban areas are furnished and interpreted in terms of a hypothesis presented in Sutherland’s paper.Subject Classification: 50.50; 28.45; 50.75.

A Consultant's View of the U. S. Department of Housing and Urban Development's Noise Standards (HDD Circular 1390.2)

A number of federal agencies in dealing with environmental noise specify criteria and by so doing imply a procedure by which one may assess the acceptability of a given noise environment. Based on consulting experience, a practical evaluation of the U. S. Department of Housing and Urban Developments policy in this area (HUD Circular 1390.2) is presented. In particular, the desirability of specifying a 24‐h sample time is discussed. Alternate schemes are suggested. Also, diurnal variations in noise data have been compiled and are used to compare HUDs criteria with the Federal Highway Administrations standard (PPM 90‐2).