Bare floor and echo: carpet first, or curtains first

A bare floor is the first thing to fix in a hard room, and curtains are usually the second. Floor area is larger and closer to the source.

The room that rang

Nadia’s office was a converted dining room with laminate over concrete and one window. Clapping produced a fast flutter that died in under a second.

On calls her voice sounded loud and slightly metallic, as if she were talking into a tin. Colleagues asked whether she was in a bathroom.

She assumed the problem was the microphone and bought a better one. The new microphone recorded the flutter more clearly, which was not progress.

What a hard floor does to a voice

A hard floor reflects almost everything that reaches it, and it is the largest uninterrupted surface in most rooms. The reflection arrives early and loud.

Early reflections fuse with the direct sound and change its tone rather than adding an echo. That is why a hard room sounds bright and thin rather than reverberant.

The floor is also close to the desk, so its reflection has the shortest path of any surface. Short paths cause the most tonal damage.

Why curtains are the popular first move

Curtains are visible, cheap and easy to hang, and they solve the problem people can see. A window looks like the obvious source of echo.

Glass is reflective, so the instinct is not wrong. But a window is a small fraction of the surface area in a room with four walls and a floor.

Nadia hung a heavy curtain across the window before anything else. The flutter shortened a little, and her voice stayed just as metallic on the next call.

What a rug actually absorbs

A rug absorbs mid and high frequencies, which is where the metallic quality lives. It does almost nothing below 200 Hz, so it will not fix a boom.

Thickness matters more than area for the low end, and area matters more for the top. A thin rug across half the floor beats a thick doormat.

Nadia’s first rug covered 2 square metres between the desk and the door. It changed the sound of her voice by an amount she could hear.

The test with two rugs

She recorded the same paragraph before and after, then again with a second rug under the chair. The second rug covered the area her voice actually hit first.

The recording with two rugs sounded closer and drier, with the metallic edge gone. The change was larger than the curtain had produced.

Neither rug was expensive, and both came from a second-hand listing. The pair cost less than the microphone she had already bought.

Where the echo actually comes from

She clapped from four positions and listened for which direction the tail came from. The strongest return came from the wall in front of the desk.

That wall was bare plaster, 3 m wide and 2.4 m high. It was a bigger reflector than the floor and it had nothing on it.

The floor had been the second largest surface in the room. Fixing both in order of surface area would have saved her a wasted purchase.

Ceiling and the fourth surface

The ceiling is the surface people forget, and in a low room it is close to both mouth and microphone. Nadia’s ceiling was 2.4 m, plain and hard.

She could not treat it, because the room is rented and the ceiling is not hers. A tall bookshelf reduced the ceiling’s contribution indirectly by breaking up the space.

This is the usual compromise in rented flats. You treat what you can reach and accept the rest, which leaves a floor to the improvement.

Furniture as absorber

Soft furniture absorbs more than people expect, and it also scatters sound. A shelf of uneven books is a diffuser that costs nothing extra.

Nadia moved a low bookcase to the wall in front of the desk. The clap test changed audibly, with a shorter and less focused tail.

A sofa would have done more, and there was no room for one. The bookcase was the largest soft object the floor plan allowed.

The order that worked

Rug, then wall, then bookcase, then curtain. That was the order in which the changes registered, and it is close to the order of surface area.

The curtain came last and did the least, which surprised her. It had been the first thing she bought and the last thing that helped.

Order matters because each step tells you whether the next one is worth doing. Buying everything at once hides which item worked.

What each item cost her

The two rugs came to about forty pounds, the bookcase was already there, and the curtain was thirty. The total was less than a single acoustic panel.

Panels would have worked faster on the wall and looked worse in a dining room. She wanted the room to still be a room.

This is the trade with soft furnishings: slower gains, no drilling, and a result you can move out with. Rented rooms reward that.

The limit of soft furnishings

Soft surfaces absorb the top end and leave the low end, which can make a room sound dull rather than dry. Too much soft furnishing is its own problem.

Nadia stopped when the room sounded slightly dead on video and normal in person. That is the balance most people are actually looking for.

Below 100 Hz nothing she did made any difference at all. Footsteps from the flat above still arrived through the ceiling and the side walls.

How to tell you are done

Clap once and listen for the tail of it. If the tail stops within a quarter of a second, the room is dry enough for speech.

Then record a sentence and listen on headphones. A room that sounds acceptable in the speakers can still be obviously hollow on headphones.

Nadia’s last recording needed no processing beyond a level adjustment. That was the point at which she stopped buying things for the room.

If a rug under the chair does more than a curtain over the window, why does the curtain get bought first every time?