POLA

Based on an idea by Anke Eckardt, the PO­LA re­search pro­ject cen­ters on the de­vel­op­ment of a new sys­tem for the at­ten­u­a­tion of low-mi­drange and bass fre­quen­cies, fea­tur­ing lightweight uni­tized con­struc­tion cus­tomiz­able to any in­door or out­door lo­ca­tion.

The sys­tem com­bines two seem­ing­ly dis­sim­i­lar ma­te­rials: air, a sound-pro­p­a­gat­ing medi­um that al­so hap­pens to be the mix­ture of gas­es in the at­mo­sphere (1 m³ = 1.293 kg) and (U)HPC, or (ul­tra) high-per­for­mance con­crete, a lightweight con­crete com­posite with a refined aes­thet­ic. This mar­ri­age of sculp­ture and func­tion is the fun­da­men­tal idea be­hind PO­LA.

Func­tion

To cre­ate this nov­el sound­proof­ing sys­tem, the PO­LA pro­ject com­bines the func­tio­n­al­i­ty of a Helmholtz re­s­o­na­tor with a new de­vel­op­ment in the field of en­gi­neered con­crete. By acous­ti­cal­ly op­ti­miz­ing the sur­faces of tex­tile-sheathed (U)HPC, the re­sult­ing re­s­o­nance ab­sor­ber can be made to cov­er the ne­ces­sary band­width. This sys­tem owes its unique ef­fec­tive­ness to an in­ven­tive method of cre­at­ing acous­tic macro- and mi­crostruc­tures:

• Macrostruc­tur­ing A num­ber of re­s­o­nance ab­sor­bers tuned to vary­ing fre­quen­cies are para­met­ri­cal­ly com­bined so that their over­lap­ping band­widths pro­duce the broad sound spec­trum ne­ces­sary for ef­fec­tive noise re­duc­tion. To­gether, the re­s­o­na­tors that make up the com­po­nent form a site-spe­cif­ic sound-ab­sorp­tion struc­ture (= macrostruc­ture) in the form of an ir­reg­u­lar hon­ey­comb. The size and dis­tri­bu­tion of the cells is cal­cu­lat­ed on the ba­sis of site-spe­cif­ic mea­sure­ments and in­te­grat­ed in­to con­struc­tion by means of an in­no­va­tive con­crete-form­ing sys­tem. The hon­ey­comb struc­ture is not on­ly high­ly acous­ti­cal­ly func­tio­n­al but al­so per­forms ex­treme­ly well in the crit­i­cal area of wind load re­sis­tance (both pos­i­tive and neg­a­tive).

• Mi­crostruc­tur­ing The cell struc­tures are built from a new type of acous­ti­cal­ly op­ti­mized open-pore (U)HPC that is en­gi­neered to have a low Q fac­tor (qual­i­ty fac­tor) and thus a high band­width. While (U)HPC has ex­cep­tio­n­al struc­tu­ral qual­i­ties, its sur­face is typ­i­cal­ly very smooth, mak­ing it a poor ma­te­rial for noise abate­ment. A method de­vel­oped by Build­ing Art In­ven­tion and in­cor­po­rat­ed in­to the form­ing pro­cess has made it pos­si­ble for the first time to pro­duce (U)HPC with a high­ly porous, acous­ti­cal­ly op­ti­mized sur­face; this method is used on the in­sides of the ab­sor­bers.

The PO­LA sys­tem is a self-sup­port­ing el­e­ment; thanks to its uni­tary con­struc­tion and free­dom from ex­ter­nal sup­ports, it is an ide­al ma­te­rial not on­ly for build­ing in­te­ri­ors and fa­cades, but al­so for noise bar­ri­ers along high­ways and high-speed rail lines, where it can with­s­tand the ex­treme wind loads pro­duced by pass­ing traff­ic.

Sculp­ture

The com­bi­na­tion of air and con­crete pro­duces hol­low cav­i­ties, each of which has a vol­ume. Be­ing a three-di­men­sio­n­al ob­ject, an air-filled na­t­u­ral cav­i­ty can serve as sculp­tu­ral ma­te­rial. The myri­ad com­bi­na­tions of vol­umes and shapes gives rise to an in­ex­hausti­ble ar­ray of forms in space. With the ad­di­tion of open­ings, th­ese forms can be made to pro­duce a va­ri­e­ty of “tun­ings” like those used in the long tra­di­tion of mu­si­cal-in­stru­ment mak­ing, “col­or­ing” the sur­round­ing space on the au­di­to­ry lev­el and cre­at­ing an aes­thet­i­cal­ly dis­cerni­ble SON­IC SPACE.

With this blur­ring of the line be­tween the artis­tic and the func­tio­n­al comes a de­hierarchiza­tion or even dis­so­lu­tion of the art ob­ject “in favour of a vivid acous­tic to­pog­ra­phy” that is ex­pe­ri­enced more as a to­tal land­s­cape. It is a con­cep­tion of ar­chi­tec­ture “not on­ly as an en­clo­sure of space but as a sys­tem of thresh­olds reg­u­lat­ing the re­pul­sion, in­ges­tion, and ex­pul­sion of en­vi­ron­men­tal el­e­ments, not least of which (is) sound,” with ears that are “in a con­s­tant and pro­duc­tive dia­logue with the walls, thresh­olds, and spaces” around them.(1)

(1) Niall Atkin­son, “Think­ing through Noise, Build­ing to­ward Si­lence: Cre­at­ing a Sound Mind and Sound Ar­chi­tec­ture in the Pre­mod­ern Ci­ty,” in “A­cous­tic Moder­ni­ty,” spe­cial is­sue, Grey Room, no. 60 (Sum­mer 2015): 12.