Sound in the home

 Last week I had an online meeting with one of my students who, after a couple of minutes, asked: "Are you in your office today?" An odd question, but one that set me thinking -  I usually hold our online meetings from home, where the WiFi is more reliable, so what was it about the background sounds that prompted his question? He was quite sure about its being the echo - my office has entirely hard surfaces, giving a quite different background acoustic environment.

My living room, where I have my normal online meetings, is probably less sound absorbing than most people's, as I have no carpet (due to allergies) and my furniture is not particularly sound absorbing, but clearly the presence of curtains and upholstered seating is enough to make a noticeable difference.

My living room with limited soft furnishing, but wooden floor and high ceiling

In spaces that are very reverberant and echoing, we tend to be more alert and energetic, while in more sound-absorbing spaces, we tend to feel more relaxed. While acoustics is a highly developed field of engineering, especially for spaces designed for specialised sound applications such as concert halls, opera houses and lecture theatres, we tend to take a more intuitive approach in domestic design.

The two key tools to acoustic control are shape, and porosity or surface texture. Concert halls and lecture venues often use curved shapes (especially the ceiling) and splayed surfaces (often the side walls) to "shape" the sound reflection patterns, so that it is optimal for the performers and gives every seat in the audience an equivalent experience, as far as possible. An interesting aside is that a concert hall specifically for chamber music and small groups will often have mainly hard (and highly sound reflective) surfaces to amplify the sound, whereas venues for full orchestra will use curves and more absorbing finishes to help to blend the sounds of the many instruments.

So how does this help us in home design? One often hears of people singing in the shower, but it seems that singing in the bath is less of a "thing". The answer to this is that a shower has many acoustic features that are different with a bath: the shower is a very small space, with a hard floor and often tiles on the walls, and a glass shower door, which will also amplify the sound. All the sound waves will reflect back to your ears with minimal loss of energy, making your voice sound like a rock star or opera singer! By contrast, while the rest of the bathroom will often have similar hard finishes (tiled walls and floors, or very smooth plaster walls), the distance to each of the walls is much greater, giving a longer reverberation time with greater energy loss, and a really significant difference is the water in the bath, so your voice will be more muted than in the shower and less spectacular.

My bathroom has entirely hard surfaces: even the blind for the window is of a hard fabric

In our living and sleeping spaces, we will probably want a much more sound absorbing room, so we tend to use more absorbing materials and fittings. The addition of a carpet or thicker curtains can often make a big difference to the acoustic "feel" of the space for relatively little cost. The addition of scatter cushions and throws will have a similar effect. In an open-plan layout, the space will often be quite reverberating, or you may even find it creates some annoying acoustic effects, such as sound bouncing from the kitchen area into one corner of the sitting space. A screen of sound absorbing material or a porous material creating a dropped ceiling are relatively simple ways of "tuning" the space. 

In a domestic setting, a good approach is to do things incrementally, with maybe a clear colour scheme to guide you when adding elements. At a certain point, the room will "sound" just right, and more soft finishes will tend to dull the sound, making conversation or your sound system too muted. In a bedroom, though, one can normally go wild with the sound absorbing elements to enhance your feeling of relaxation and quiet during the night. 

In contrast with my living room, my bedroom has many more soft furnishings, even some small rugs

The one item in the home that deserves special treatment is if you have a piano or other large musical instrument in a fixed position in the house. Here, the sound performance of the instrument is greatly enhanced by the simple addition of a carpet directly under the instrument. Try this for a few weeks and see whether you need to damp the sound further: you may want to put a couple of hangings or tapestries on the closest walls, or have an area of dropped ceiling directly above. These will prevent reverberation, so you will lose some volume, while eliminating secondary wavelengths being generated by the surfaces. You can also use these tricks with a sound system that doesn't sound quite right in your space: again, do this incrementally so that you can optimise the volume and echo characteristics.

Even though the room already had a carpet, my daughter introduced another when she got her piano

Another aspect of sound in a domestic setting relates to those of us who live in apartments and town houses: our neighbours! You may have found that your own neighbour has an intrusive sound habit, such as talking on a cell phone at the boundary with your property, just next to your workspace, requiring you to keep all the doors and windows shut even in mid-summer. Your neighbour could listen to the radio when showering, so that you get the "morning show" every day - the sound amplification from singing in the shower applies equally to a radio, plus it is often set to maximum volume to be audible above the gushing water!

If you are concerned about your own noise generation or your neighbour has complained to you, there are a couple of very simple tricks. For the bathroom, keep the window shut while showering, but open it immediately after to let out the steam so that you do not start a mould ecosystem in your bathroom. For the piano (especially an upright, if you need to have it against the party-wall adjoining your neighbour) my sister's piano teacher had a brilliant and inexpensive strategy: the bottoms of egg boxes fixed to the wall with double-sided tape in the space behind the piano. Here it is a good idea to trim the boxes so that they are not visible beyond the back of the instrument, as it is not the most aesthetic solution. You want to avoid painting the egg boxes, as its effectiveness comes partly from the small pillows of static air formed by the shape of the surface, but also the porosity of the box itself - paint will tend to seal off these tiny air spaces that are sucking up the sound.