{"id":2816,"date":"2026-07-22T13:56:12","date_gmt":"2026-07-22T11:56:12","guid":{"rendered":"https:\/\/stage.dekozell.de\/?p=2816"},"modified":"2026-09-25T12:18:11","modified_gmt":"2026-09-25T10:18:11","slug":"improve-room-acoustics","status":"publish","type":"post","link":"https:\/\/dekozell.de\/en\/improve-room-acoustics\/","title":{"rendered":"Improve Room Acoustics: Reduce Echo & Reverberation"},"content":{"rendered":"

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Basics & Room Acoustics<\/div>\n

Improve room acoustics: why rooms echo and what really helps<\/h1>\n
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\nAuthor:<\/strong> Thomas Neubauer, Managing Director of DEKOZELL, has 20 years of experience in the development and application of acoustic plaster. He personally reviews and takes responsibility for every article.<\/div>\n
\n22 July 2026<\/span>
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\n7 min read<\/span><\/div>\n<\/div>\n
\"Graphic:
Reverberation is rarely perceived as a distinct sound. Instead, you notice it as strain: the sound continues while the next sentence is already being spoken.<\/figcaption><\/figure>\n

A room can be perfectly furnished and still feel uncomfortable. As soon as two people start talking, words become hard to understand, every footstep sounds too loud, and a phone call turns into a test of patience. Room geometry also plays a role: unfavourable proportions can make low frequencies boom or create higher-frequency flutter echoes. But the everyday problems you actually notice\u2014blurred speech and every sound seeming too loud\u2014are mainly caused by hard surfaces and the reverberation they create. Both can be improved in a targeted way once you understand where the reverberation comes from.<\/p>\n

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At a glance<\/div>\n
Rooms reverberate because hard, smooth surfaces reflect almost all of the sound. Carpets, curtains and upholstered furniture take some of the harshness out, but quickly reach their limits in larger rooms. If you want to reduce reverberation time permanently without adding visible technical elements to the room, seamless acoustic plaster on the ceiling or walls is the logical solution.<\/div>\n<\/section>\n
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Why modern rooms reverberate so strongly<\/h2>\n<\/div>\n

Sound is movement through the air. You can picture it like a Newton\u2019s cradle: when you move the outer ball, the impulse travels through the entire row while the balls in between barely leave their positions. In the same way, air molecules pass sound energy from one neighbour to the next without the air itself travelling across the room.<\/p>\n

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When this movement hits a surface, it is either absorbed or reflected. Hard, smooth materials reflect almost all of the sound, while soft and porous materials absorb it. Modern architecture relies heavily on hard, smooth surfaces: large areas of glass, exposed concrete, polished floors and bare walls. These materials look good\u2014but acoustically, they are the problem.<\/p>\n

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Hard surfaces reflect almost everything<\/h3>\n

In a room with lots of glass and concrete, sound loses very little energy. It bounces from surface to surface, overlaps with itself and continues for a long time. Clearly spoken sentences turn into a blurred mix of sound because the original sound and its reflections reach the ear at the same time.<\/p>\n

Reverberation time: the invisible measurement<\/h3>\n

Acousticians describe this using reverberation time. It indicates how long a sound takes to decay significantly. The longer this value, the more reverberant the room feels. Excessive reverberation makes speech difficult to understand and demands more concentration in everyday life\u2014whether in a living room, restaurant or open-plan office.<\/p>\n

What about the floor plan? Room modes and flutter echoes<\/h3>\n

A fair point: room geometry matters too. Standing waves, known as room modes, form between two parallel walls. The lowest mode occurs when exactly half a wavelength fits between the two surfaces.<\/p>\n

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Formula for the fundamental mode<\/div>\n
f = c \u00f7 (2 \u00d7 d)<\/div>\n
f<\/b> Frequency of the lowest mode in hertz<\/span>c<\/b> Speed of sound, around 343 m\/s; in warmer air, closer to 360 m\/s<\/span>d<\/b> Distance between the two parallel walls in metres<\/span><\/div>\n
Example:<\/b> With a wall spacing of 3.6 m, the fundamental mode is around 48 to 50 Hz\u2014a deep bass tone. Its multiples follow above that, roughly around 100 Hz, 150 Hz and so on.<\/div>\n<\/section>\n

It becomes critical when length, width and height have simple integer ratios. The modes of several axes then coincide at the same frequencies, reinforce one another and make some bass notes boom while others almost disappear. That is why rooms are deliberately planned with irregular proportions rather than as cubes or simple multiples.<\/p>\n

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Low frequencies<\/div>\n
Room modes<\/div>\n
Depend on the proportions of the room. Some bass notes boom while others almost disappear. Thin surface treatments can barely control them; intelligent room dimensions and targeted low-frequency absorption are what help here.<\/div>\n<\/div>\n
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Mid and high frequencies<\/div>\n
Flutter echoes<\/div>\n
Occur between two hard, smooth surfaces directly facing each other. Sound bounces back and forth and creates a metallic, fluttering decay. A single hand clap makes it easy to hear.<\/div>\n<\/div>\n<\/div>\n

The distinction matters in practice because the two problems require completely different solutions. A flutter echo is relatively easy to eliminate: interrupt one of the two parallel surfaces with an absorbing or diffusing surface.<\/p>\n

Important distinction<\/b>Deep room modes require genuine low-frequency absorption, such as a concealed bass trap. The DEKOZELL\u00ae Acoustic Plaster System DISTANCE-Easy<\/a> is designed for exactly this purpose: without the airtight rear facing and completely backed with around 20 cm of mineral wool, it reaches significantly lower frequencies than a thin surface layer while still looking like a normal wall or ceiling.<\/div>\n

What makes speech sound blurred and every noise seem too loud in everyday life belongs to the second group: broadband reverberation in the mid and high frequency range caused by hard surfaces. And that is precisely what absorbing surfaces remove from the room.<\/p>\n

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How to recognise a reverberant room<\/h2>\n<\/div>\n

You often notice the problem before you can put a name to it. Typical signs include:<\/p>\n