Perspective

Musical perspectives on acoustics

Good Acoustics depend on which type of music is to be played. A rock band does not sound good in a symphonic hall while classical music doesn’t work at all in a rock venue.

Still, all kinds of music is being performed in most halls which is why there is a need for altering the acoustics to suit a given type of music.

It all starts with the musician making sounds on his or her instrument.

From there, let’s take a look at what makes a hall work well acoustically for various types of music.

At an amplified music concert in a hall with appropriate acoustics for the purpose and a professional sound engineer, the musician feels connected with his or her instrument, with the sound of the colleagues’ instruments as well as with the audience.

Playing feels easy and the musicians can address their attention to the main reason why they took the effort to come to the venue: to give their audience a great experience.

In such a sonically favourable environment, the sound coming direct from each instrument gets through to the band members with clarity. Stage monitors and some sound-reflective surfaces around the stage makes it easy to play together. This sound reflected off of surfaces around the stage is called early reflected sound, or early reflections, since it arrives sooner at the musicians ears than sound reflected from surfaces further away in the hall.

Seeing and hearing the reaction of the audience makes playing an even better experience. The sound of the audience gets louder on stage if some surfaces in the audience area reflects the sounds they make.

However, sound reflective surfaces in the audience area will also reflect the sound coming from the PA system which in bigger venues is the loudest sound source.

This reflected sound arrives late on stage and it can be quite distractive, if it is loud compared to the earlier sound as encountered by the musician.

So if the late sound is too loud compared to early sound on stage, the performance is apt to be a less pleasant experience for the musician.

Higher pitched sound such as cymbals, the upper range of keyboards and guitars etc. as well as overtones from the instruments are easy to direct from the PA speakers at the audience because of loudspeaker directivity at these frequencies. And since the audience absorbs these high frequencies, they are not reflected back to the stage, these are seldom causing problems.

The lower pitched sound, for instance the low registers on guitars and keyboards, male vocal as well as bass and drums however, is emitted from the subs and speakers in virtually all directions and even the portion of it that is sent directly onto the audience is not absorbed by them unlike the higher pitched sound. An audience absorbs 4-6 times more, higher pitched sound than lower.

Using in-ear monitors helps shifting this balance somewhat, so that direct sound gets louder than, and better masks, late reflected sound. Unfortunately the audience reactions and the stage-reflections are also dampened by the ear plugs. And although this is compensated for by dedicated microphones picking up this sound and added to the in ear mix the late, boomy, bassy sounds are not really blocked by the in ear plugs and is furthermore sensed through the body of the musician.

When this late, reflected boomy sound is loud, musicians want their monitor level turned up to overcome it. It was proven scientifically, that late low pitched sound, also called low frequency reverberation, is what makes a hall inappropriate for amplified music such as pop, rock and jazz. Therefore, the trick is to dampen the low frequency reflected sound. In other words: quite large surfaces in the hall need to be capable of absorbing low frequency sound to achieve a low reverberation time at low frequencies.

It is not the sound level of the lower tones in general that needs to be less loud – only the reflected low pitched sound.

Furthermore, this unwanted effect of too much sound arriving on stage also initiates a chain reaction, an evil spiral so to say, since the musicians will ask for louder levels from possible open monitors on stage to overcome the late sound. Then these loud levels of unprocessed sound will hit the audience, the sound engineer and his mix of carefully processed sound.

This leaves the engineer with little choice other than increasing the PA speaker level again. Unfortunately this also creates even louder late reflections on stage which results in an unfortunate evil spiral. This is the logic explanation for sound engineers wanting to deaden the stage. Needless to say this is not a good solution since it lowers the level of the early, more defined sound the musicians depend on.

The solution for the challenge is to get the right level of reverberation time, which is the time it takes for the sound to die out, especially at low frequencies. And the stage area must not be “a separate room” compared to the audience area. The acoustics of the two spaces must be similar. They must be balanced. Flex Acoustics has through research set forward recommendations on suitable reverberation times at various frequencies and hall sizes for amplified music.

Fortunately, such acoustics are also what the audience favours. An amplified music concert in a hall with a much too long reverberation time will make the music almost incomprehensible since the rhythmic backbone of the music is transformed into a long, blurred continuum of muddy sound. This is not acceptable! Now, a 5% increase of ticket/bar prices will increase sound quality tremendously. Which audience is not prepared to pay that in return?

Classical Music

At a classical concert, in a dedicated classical music hall, there is no PA system and no electric amplification of the instruments. The musicians must create enough level on their own for the hall to carry the music out to the audience. This calls for the hall to NOT absorb sound, but rather reflect it so that the sound level is not decreased.

This, and the fact that for instance symphonic music and especially choir simply sounds good in a reverberant hall, where the sounds are allowed to bounce between surfaces for quite some time, makes a classical music hall acoustically quite different from a hall for amplified music. Unlike the hall for amplified music it is really important that the hall by itself carries out also the bass sound. The director’s job “gets easier” if the hall by itself balances the instrument groups appropriately in relation to each other. Such a hall is musical by itself for the given purpose.

And again, the performer needs the right balance between early reflected and later reflected sound. With a lack of early sound the performer will not be in contact with his or her own instrument nor the sound of his colleagues.

With a lack of late sound she will not be able to feel a contact with the audience and will have to use too much power in order to create the level that the director asks for.

Since especially late arriving sound must be dampened significantly at bass frequencies to make a good classical hall work well as a rock venue, bass absorption was the aim when inventing, developing and designing the aQflex absorber system.

Today, it is the only variable acoustics system to do exactly this job, and it even does not absorb the high frequencies which are taken care of by the presence of the audience. That leaves the hall with a transparent sound with great dynamics for both classical and amplified music. Incorporate the aQflex system in a hall well designed by an acoustic consultant. You will get perfect acoustics for every event.

Read more about the aQflex system.