KILLING NOISE.

Hawera Star, Volume XLIX, 31 August 1929, Page 11

KILLING NOISE.

U’SE OF SKA-GRASS. 'pi!E varieiy of sea-grass, which is known to botanists as “zostcra marina.” and common in- sliallopv waters ail round coasts, when dried, has tin' extraordinary quality of killing sound, as well as being an effective insulator against heat and cold, says a correspondent of the “San Franciscoi Chronicle. ’’ On this account it is being used increasingly in house construction. Besides deadening sound, sea-grass does not harbour insects and is practically non-inflammable. It is also used extensively in upholstery and mattress making.

To prove its efficiency as a sound deadene’r. an experiment may be made with an alarm clock and a box lined, lid as well as sides, with the material. Set the alarm going, put the clock in the box. and drop the lid. The sound stops instantly. Open the box and the alarm is heard again. This quality is said *to be common to all loose, fibrous, or cellular substances.

Tiles which absoro sound have also been developed. They arc made of metal in the form of trays sixteen inches square, • and perforated so .that sound ! passes through them just as it doer through a screen window. The frays are packed with a felt-like, sound-absorbing material, which is said to consume 70 per cent of the noise.