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Its long been the case that the public perception of what we do has been very different from our image of ourselves.When I worked briefly as a sound engineer for a small cabaret performance, an artist insisted on calling me "sparks". The general perception is that sound engineering is predominantly about electrical knowledge. I think this may be why so many sound engineers had ponytails. To distinguish them from electricians and align themselves with the creative side of the music industry. I have been excluded from the ponytail fraternity as I am follicly challenged. I have had to argue that we are different because I cannot demonstrate it with creative hairstyling.

Perceptions change. Now the problem is that building contractors and venue managers see sound design as part of the IT industry. It is true that sound is transmitted around a venue as data and because of this sound engineers need a good understanding of IT and data transmission skills. But once the transmission has reached the loudspeakers, acoustics becomes the dominant discipline.

Sound engineers will never become just IT people, because they need to understand dynamic range, limiting, compression, masking, speech intelligibility and other sound engineering concepts. But most of all they need to understand what happens when the sound leaves the loudspeaker and that is acoustics.

A recent audio troubleshoot in a city meeting room, led to the discovery of an incorrectly wired aerial distribution system. The interconnections resulted in several diversity radio microphone receivers, getting the rf input from only one aerial into their A & B aerial inputs. Guess what? It did not work as a true diversity system resulting in signal level fluctuations.

I had to smile when I thought of the hours of intelligent design followed by hours of painstaking electronic engineering in order to make the first diversity receiver, and how it was all nullified in a few moments of unfocused action by a well meaning installation contractor.

But this is indicative of what I perceive as a far bigger problem; the disconnect between the design of products and the user of the product, in this case the installer.

The connection between the designer and the user is the, often frustrating, user manual, written by an intermediary - a technical writer. I notice that some products do not come with user manuals anymore. If you need to understand them, load a CD or go on-line. As technology becomes more sophisticated the need to understand a product becomes increasingly relevant and more difficult. Will all products have a small LCD display built-in which accesses the user instructions? Perhaps the user manuals will all be available on-line for us to access when required? Sometimes, as with an amplifier I recently encountered, the product was built in China but the DSP programming was done in USA resulting in a product with only partial instructions. Either way it is important that the user of a technologically advanced product gets a GOOD, CLEAR, CONCISE description of how to use all a product's facilities. Better still, lets make the device itself so intuitive to use with colour coding and clear labelling, that we do not need to access the manual all the time. I know some people who would prefer not to read a manual at all!

I have just completed an audio recording project that required an unattended recording of a crowd at a football match. I wanted to record to solid state memory but the recording would need to be up to 3hrs long with reasonable quality, (at least 44.1kHz, 16 bit). Many recorders are intended for multiple takes in small files. I required a long recording time in a single file. FAT32 files have a maximum file size of 2Gb which could be a limitation. An NTFS file system would be required to give the security of a bigger 4Gb file size. Also, I did not want the batteries to be exhausted before the recording was completed, especially as I wanted the recorder to provide 48vdc phantom power to our two microphones. The next problem is the dynamic range of an excitable football crowd! How could I set the record levels in advance?

The solution to this was a Fostex FR2-LE recorder which records to Compact Flash card. It can use NTFS to give 4Gb file size although this option has to be selected from the menu. The standard AA alkaline batteries would not guarantee enough recording time but a large capacity Ni-Mh battery pack can be obtained to give longer recording times. Usefully, the machine has an Auto Level Control which could help tame the dynamic range of furious fans. Finally, it can supply 48vdc phantom power to the microphone inputs to power our Sennheiser 416 microphones.

In the end the file size was only 1.5Gb, the battery pack was not pushed anywhere near its limit and the ALC did its job beautifully. The recording was done in some extreme conditions as it snowed continually all afternoon and several shovels of snow got dumped on our equipment cases, but the combination of Fostex recorder with Sennheiser mics and some Rycote wind-shields got the job done perfectly.

The Digital Dividend Review has brought upheaval to users of wireless microphones. We have spoken to clients who are abreast of the changes and some (even at this late stage) who are only just learning about them. I feel sure there are those who are still unaware of the frequency changes.

While implementing a change of frequency for one of our clients we used a frequency scanning system to find out what other transmissions were occurring at that location. It turned out to be a very useful exercise and a service I feel could be useful to other people. Several problems can occur with radio microphone transmissions and to be able to correctly assess and remedy a problem it is important to know what is happening and not just guess at the probabilities.

A typical RF scan
A typical RF scan

We can scan a wide spectrum of frequencies or just a particular channel, and then provide a plot. We can also compare signal strengths for different aerial systems or locations. It gave me a whole new insight into wireless microphone reception at the location where we were working and we could do the same for you.

Contact us for more information on 01727 756999 or via our website

Acoustic modelling of rooms and their sound installations has become a common part of our industry and possibly one of several reasons why installations have improved in sound quality.

Recently I have listened to two industry professionals giving strong views on the relevance of acoustic models.

The first indicated that acoustic modelling is capable of giving very accurate predictions. Sometimes the predictions are more accurate than real life measurements can replicate.

The second indicated that sound system designers rely on acoustic models to support their assertion that their engineered solution was the only suitable one. (Both views have been pr├ęcised here so apologies if I have changed the emphasis at all).

I think both views are relevant and not as contradictory as they might at first appear. Most experienced sound designers know intuitively how standard loudspeakers and their placement will work in a given environment. In these situations, acoustic modelling is useful to convince the client that the sound designer knows what he or she is doing.

Where acoustic modelling comes into its own is when the sound designer wants, or needs, to try something less conventional. The acoustic model can really show up the pros and cons and highlight potential problems. By playing with the model the sound designer can try different options in a way that he or she is never likely to experience in a real world installation. This way they may be able to produce a sound system design where loudspeakers are better integrated into their environment or where less conventional loudspeaker types are used to good effect.

I have spent much of the last few weeks checking a football stadium and its many and various sound systems. We have also been upgrading some areas where building work has taken place. I have found one or two pieces of test equipment invaluable for this work.

The GoldLine ZM2 is basically an impedance meter but its high output, interrupted, tone will drive a 100v loudspeaker line. It has been brilliant for helping us locate circuit breaks in loudspeaker chains. Provided the installation is in a basic chain configuration you just follow the tone along the chain until you come to a loudspeaker with no output. It is not quite so easy with a star configuration but it still helps you locate the likely area for the circuit break.

Whilst equalising areas of the stadium sound I have been using the NTI MR-PRO signal generator. Having previously used the Minirator for this job I find the addition of a Mute button on the MR-PRO very beneficial. By using the Mute button I could communicate with the person at the analyser position (stadium lawnmowers allowing) before restoring the pink noise to its original level. The MR-PRO was also able to replay WAV. files of the stadium announcers voice allowing us to check the overall sound quality for naturalness.

Thankfully everything is now signed off. It only remains for the football team to do their bit on the pitch!

We have recently completed the design and installation of acoustics for the UK demonstration facility of a professional loudspeaker manufacturer.

Experience has shown me that although a near anechoic room would provide some of the best listening detail, demonstrators and their customers are sceptical of listening in an environment which is clearly not "real world".

Designing the demo room acoustics to give reasonable amounts of diffusion and absorption was our goal and we were very pleased when the measured results came extremely close to our predictions.

Evaluation over a period of time should confirm the ultimate success of our acoustic design but it certainly worked for me; I bought the client's loudspeaker we were using to evaluate the room!

What is the ideal reverberation time for a church? There are a couple of factors to take into account.

The first one is the type of worship that the church enjoys. Many churches have a combination of traditional services and modern worship, so this will require some compromise.

The second factor is the volume of the church. Bigger spaces naturally have a longer reverberation than smaller spaces and that fits with people's expectations.

My preference is to keep the reverberation time short enough so that speech can be easily understood which will also help with musical detail, but always retaining enough reverberation to make participants feel they are part of a community and encouraging them to sing. This is not an easy compromise to achieve but worth some considerable effort on our part in order to get the best possible balance.