Expansive visions and the desire to give each structural element a distinctive character often involve considerable practical challenges, not the least when it comes to the acoustical environment. In other words, the challenge of limiting noise and its associated health problems.

In addition to reduce noise or unwanted sounds from, for example, nearby traffic or adjacent premises which falls under Blocking in the ABC of Acoustics, you also need to address the A for Absorption and C for Cover. The challenge of absorption includes the desire to achieve good so-called speech intelligibility. Often measured as the Speech Transmission Index (STI), which is a number between 0 and 1 where 0 is poor and 1 is good. You get good speech intelligibility if you have a sound environment that enables relatively short reverberation times. Reverberation time is simply the time it takes for a sound impulse to be absorbed and disappear. The STI in such areas is generally speaking greater than 0,6.

If you are in a room or space with long reverberation times, you get the effect that the sound takes a long time to disappear. The sounds that are in the room will then “wander around” until they have ebbed out. Sounds that have been wandering around for a while can sometimes hit the eardrum at the same time as other sounds. The ear then finds it difficult to distinguish these and be able to interpret the messages, which are individually understandable but together become a murmur. The speech intelligibility is poor and the STI is low.

Often the first thing you lose is consonants and eventually you have lost so many consonants that you need to be born in a consonant-heavy part of the world to even have a chance to interpret the incoming sound. Compare with how it sometimes sounds in old stairwells.