Variable acoustics and acoustic enhancement


The SIAP system enhances the acoustic of a hall for a single purpose and/or multipurpose use:

Single purpose SIAP acoustic enhancement can for example be improvement of the acoustics for music in a theater, concert hall, opera house or church or intelligibility of unamplified speech in a drama theatre. 

Multipurpose SIAP acoustic enhancement makes the acoustic of a hall optimally adjustable to a wide range of purposes, in short: unamplified, amplified music and cinema surround support. For example the acoustic for music can be improved by enhancing the Reverberation Time, envelopment of the sound, spaciousness etc. of a hall that has insufficient reverberation for (classical) music: operetta, opera, ballet, recital, chamber music, chamber orchestra, symphony orchestra, choir, organ etc. But also for rooms where the acoustics are so dry that even the amplified performances (pop/jazz/play/musical) sound dull and / or when there is a lack of interaction with the audience, the acoustic can benefit from more support to achieve a nice room ambiance or “liveliness”. Variable Acoustics (also called: VAS – Virtual Acoustic System and AAS – Active Acoustic System and EAS – Electronic Acoustic System – Acoustic Enhancement or variable acoustic system), are in general much more efficient and economical then creating a variable acoustics via physical and mechanical solutions.  Electronic enhancement systems are today widely accepted due to the high sound quality which has proven itself the last decade.

The SIAP system is unique because the reverberation which is generated by the processor to increase the reverberation time of an auditorium, is composed of sound reflections like in a real concert hall or opera theatre.

In other words, SIAP reverberation is fully natural (contrary to artificial reverberation processors and/or acoustic feedback based systems which can sound unnatural or “amplified”). As a result of this natural process the SIAP system is patented worldwide.

Theatre acoustics

Theatre acoustics

Theatres are generally built with a short reverberation time, since this is required for good speech intelligibility and is the optimum for amplified sound. Many venues are made as acoustically “dry” as possible because most performances are fully amplified. For reinforced sound a reverberation time somewhere between 0.7 and 1.2 second is ideal. Many elements in a theatre determine the acoustic. Walls and seats can for example provide plenty of absorption and non-parallel walls are an effective means against flutter echos and other undesirable reflections. In addition to the reverberation time there are of course numerous other acoustic parameters which influence the acoustic quality and sound of a theatre auditorium.

Critical spots

In a theatre auditorium – which possesses a beautiful ambience – “difficult” positions can be found.
One can think of under balcony seats (impedance step) or the stage area (side and/ or rear wall reflections). Or a slap-back from the auditorium rear wall or balcony front edge back to the stage. In an acoustic design all these subjects are taken into account to realize an acoustically well-performing theatre.

SIAP ambience

In a theatre which has a reverberation time of 0.7 to 1.0 second, the acoustic is rather dry. As said, this is an ideal characteristic for amplified music (and speech), but it’s not really a friendly or pleasant atmosphere to be in. When one walks from a foyer space (which usually has a pleasant acoustic atmosphere) into the theater hall, conversations etc. suddenly sound “dead”. To begin with SIAP can provide a very pleasant atmosphere, which makes the experience of entering the auditorium a less “hard” transition. The SIAP “theatre ambience” can be active 24/7; it’s not the reverberation time that is increased but the desirable pleasant reflections that are characteristic for a theatre are augmented by the SIAP loudspeakers that are (invisibly) installed.

SIAP variable acoustics & surround sound

For widening the range programmable performances in a theatre, variable acoustics and surround sound can be provided as well as theatre ambience. Variable acoustics makes the acoustic adjustable to different requirements. This gives artists as well as the audience the feeling of togetherness and being part of the performance. The audience is aware of its own presence and the artists have much less of the feeling as if they are playing into a “black hole”. Furthermore the hall is much more responsive to the artists which increases the interaction enormously. There are dedicated acoustic presets for amplified as well as unamplified music. So, from a rock/pop concert to drama, opera and classical music, but also for conference and presentations (speech support). SIAP employs a matrix which allows for a wide range of input to output settings. This way film surround sound can be reproduced as well as special musical productions. Summarizingly, SIAP offers:
1. Improved of (unamplified) speech intelligibility
2. Improved theatre ambience for the audience en with sound reinforced performances (bands etc.) without detrimental influence on the reinforced sound
3. Variable acoustics, comprising reverberation time increase and improved stage acoustics, for example:
– Opera / classical ballet (1.3 – 1.5 sec.)
– Chamber music (1.5 – 1.7 sec.)
– Brass band (1.7 – 1.9 sec.)
– Symphony orchestra (1.9 – 2.2 sec.)
– Choir (2.5 – 5.0 sec. and more).
4. Surround sound for film and theatre.

Church acoustics


The characteristic acoustics of churches can be very beautiful and desirable, on the other hand, it may have a disadvantage with speech (speech intelligibility). The origin of the churches has led to great musical compositions for organ and singing, among other things, in recent centuries.

Church and music are, as it were, ‘fertilized’. Over time, there are many churches that no longer have the desired acoustics. Often this has to do with building history (such as repair of war damage / alterations by changing use) and the acoustics of these (sometimes ancient churches) have unfortunately been lost in part. For speech, this may be beneficial for music that needs spaciousness it won’t work.

In the absence of a beautiful acoustics, the organ and choir, instrumentalists and singers of the present are not threated optimally (acoustically). They will sound too “dry” due to lack of reverberation.

SIAP has developed an integral solution specifically for churches that are too dry to get the speech (intelligibility) and acoustics (including reverberation time extension) as desired.

This solution offers both acoustics and speech intelligibility enhancement at the same time (dynamic variable acoustics). As a result, all the musicians, the speakers and the community get the nice (acoustic) experience that makes the visit to the church extra valuable. The church visit becomes a common, integral experience.

The SIAP system for churches provides high-quality speech enhancement, music playback and variable acoustics. Thus, speech amplification is an integral part of the installation. The uniqueness of this isthat speech amplification and SIAP acoustics go hand in hand. Simply put, this works like this:

When an acoustic preset is active (eg 3.0 seconds), organ, choir and vocals sound full and the acoustics “carries” the sound . But such reverberant acoustic is unfavorable to the intelligibility of speech (it’s too loud, intelligibility drops). For a good speech intelligibility, a short reverberation time is optimal, about 1 second. These are quite different – in fact contradictory – acoustic requirements. At times when a sacristan (preacher) talks into the microphone, the SIAP “voice function” is activated and simultaneous SIAP “acoustic function” (reverb extension) is automatically attenuated to optimize the speaker’s intelligibility. This is very nice because acoustics will be present at the moment of speaking, but it will automatically decrease to the right level. The advantage of this is that the acoustics don’t need to be turned off to create good intellibility. Turning off the acoustics is very undesirable, as this can be very confusing for attendees, so the space must continue to sound as it sounds.

Congregational enhancement

With some extra microphones, the visitor’s vocals are collected and included in acoustic treatment. Organ, choir and visitors are all part of the acoustics, as it should also be in a church (which is sufficiently desirable). The mutual natural balance of organ, choir and attending church members remains.

Of course, this integral solution also includes the SIAP system being linked with facilities such as the hearing aid for hearing impaired, church radio / internet and high quality (CD and / or MP3) recording. In churches where, for example, a music group (band) is performing, this automatic function can also be integrated into the SIAP system. For example, in combination with a mixer operated by a separate technician and (optionally his own speakers).
The SIAP variable acoustics works together with the acoustics of the church itself.


The microphones and speakers are as invisible as possible and (flush) mounted with a lot of respect for the interior aesthetics. In churches with a (national) monumental character, discreet integration is extra important. So no boxes against the vaults or on the walls (as far as possible). Our knowledge of church buildings and experience in this area guarantees for subtle installation.

Too much reverberation time / poor comprehensibility

Churches that have “too much” reverberation time may still be able to achieve an improvement with a well-functioning speech enhancement system. In addition, we have experience with churches in which, for example, 5.0 seconds of reverberation time, one would like to go back to 1.1 second reverberation time (eg rebuilding the building). This allows voice and music enhancement to be possible again. Subsequently, an SIAP system was then installed to provide the organ with the original 5.0 second reverberation time.

We can compile a design and advisory report based on the wishes and demands. Of course, the possibilities are also (partly) determined by any monumental restrictions, and we can advise you in this area as well.

Contact us for your specific situation.

Studio acoustics

Studio acoustics

The success of a studio depends largely on a good (recording) acoustic. A variety of starting pints and possibilities are available to achieve this. For control rooms the “live end – dead end” principle is often applied of the acoustic. The dead-end side of the room serves monitor loudspeakers which have to be able to reproduce an uncoloured sound and with correct source localizations. The live-end side of the room is beneficial for artists who are making music there. Similarly this live-end environment provides supporting ambience to the sound engineer who is giving the recording a beautiful sound. Other design principles for a wide range of applications are of course also used. SIAP can provide a useful acoustic completion.

Recording room

The recording room itself, where the music is made, not only determines the final sound quality, such as “sound stage”. Musicians prefer to experience an inspiring sounding room. Of course can acoustics be “added” to the recording during editing as a reverberation effect.

An appropriate acoustic in the recording room itself which is picked up by beautifully sounding microphones, has its advantages too.

This for the artists during music making as well as for the recorded sound. SIAP acoustic enhancement is fully natural and is therefore of course without (digital) artefacts, side-effects etc. Further acoustic enhancement during editing remains available as usual. In short, the best of both worlds.

Acoustic consultancy & design

When desired, SIAP can make acoustic design drawings and a consultancy report according to the client’s requirements, his ideas etc. Such a design will describe in detail what has to be done to achieve the desired studio acoustic. This includes sound absorption, diffusion, materialization and positioning, elimination / suppression of standing waves, HVAC noise control and building physical aspects, But also environmental noise (traffic etc.), sound emission to the neighbouring buildings etc. are taken into account. Evaluation measurements during the construction period is a most reliable way to fine-tune and optimize the design. And of course to determine if the design aims will be met upon completion. Commissioning measurements are then mainly executed for confirmation purposes and for a finishing touch. SIAP carries out all calculations and measurements for the client.