Two giant sound mirrors have been installed at King Edward Park in Hāwera.
Set 50 meters apart and facing each other, the 2.5m-tall dishes allow someone to whisper into the focal point of one dish while a friend hears the whisper at the focus point of the other dish.
South Taranaki Mayor Phil Nixon said he was very grateful to Global Stainless Artworks for donating the pieces and to the funders who made the installation possible.
"They will be a fascinating addition to our award-winning park. They are a little bit of art, a little bit of fun and a whole lot of science combined."
Global Stainless Artworks Hāwera, fabricators of high-end stainless steel balls, spheres and sculptures, has worked with the South Taranaki District Council to provide the structures for the district.
Kerry Fowler from Global Stainless Artworks said the parabola-shaped dishes collect, focus and amplify wave signals.
"Sound that originates at the focal point will bounce off the dish and travel in the direction the dish is pointing. The two dishes have been perfectly aligned so that when you speak into the focal-point ring, the sound bounces off the dish and collects at the dish on the opposite side of the lake. If you speak where the focal point ring is, your ears will also be in the perfect position for listening."
Sound mirrors - which are also knowns as whisper dishes, acoustic mirrors or listening ears - were built on the south and northeast coasts of England between 1916 and the 1930s.
They were designed to detect enemy aircraft and airships as they approached the coast, as the listener could determine the direction of the aircraft and give advanced warning to local people.
In the early 1940s the mirrors were replaced by radar.
Te Hāwera Community Board chairman Wayne Bigham said the board was "delighted to help fund such a worthwhile attraction which will provide entertainment and a sense of wonder to our park visitors".
Donations towards the installation of the sound mirrors were received from Te Hāwera Community Board, Lysaght Watt Trust, Fred and Eunice Rodie Trust, Pelorus Trust and Bizlink Hāwera.