Earthy sounds

Robin Lindner

Development engineer at VISATON.

Sound systems are also becoming increasingly important in agricultural machinery – especially since the driver's cabs are now so much better soundproofed. VISATON development engineer Robin Lindner explains in an interview what factors are most important when it comes to providing sound systems for these small cabs and how he advises the industry.

VISATON advises agricultural machinery manufacturers in various European countries. What does this cooperation involve, Robin?

We advise many leading agricultural machinery manufacturers and cab builders. I visit each one of these myself about three to four times a year. Usually there are no employees within the companies that are exclusively responsible for the sound systems, so the manufacturers are very grateful when we bring in our know-how as early as possible and advise them on-site. To this end, we install loudspeaker prototypes in new vehicle generations and test them intensively. In this way, we recognise the critical points immediately and can negotiate the installation location again or adapt the loudspeakers to the respective installation situation using special seals. This means we deliver maximum customer service, because we also take aspects of vehicle production into account.

Two broadband loudspeakers are installed in the roof of the cab – either in front of or behind the driver.
Two broadband loudspeakers are installed in the roof of the cab – either in front of or behind the driver.
In high-quality sound systems, tweeters are built into the A-pillars.
The subwoofer can be placed under or beside the seat.

Which loudspeakers are usually installed in the cabs and what aspects play a central role?

Driver's cabs are very small, which is why very special acoustic conditions prevail in them. As a result, the positioning of the speakers plays a decisive role. Ideally, they are positioned to point towards the driver. In the standard models, we usually have two full range speakers in the ceiling, on the left and right, either in front of or behind the driver. In the premium sound models, we also install tweeters in the A-pillars and a subwoofer behind, under or next to the seat.

Robin Lindner, development engineer at VISATON.

„For agricultural machinery, we've developed a subwoofer that you can connect directly to the radio.“

Robin Lindner, development engineer at VISATON.

Besides the positioning of the speakers, what other points are important here?

The loudspeakers should be attached to sturdy, load-bearing elements in the cab. If we were to mount them directly in the roof panelling, for example, which is usually made of thin plastic, this would result in interference noise and unwanted vibrations. In addition, we calculate the appropriate enclosure volume for woofers and pay particular attention to bass reflex tuning. In principle, the size of the enclosure must not be too small, otherwise it will not be possible to generate the low frequencies. The loudspeakers should be located in a sealed enclosure as this can prevent an acoustic short circuit.

Two examples of an acoustic short circuit
Missing partitions
Incorrect bolting on the partition

Acoustic short circuit – what exactly is that?

In the case of an acoustic short circuit, the air pressure fluctuations in front of the diaphragm (front sound) counteract the air pressure fluctuations behind the diaphragm, the rear sound. Depending on the size of the diaphragm area, low frequencies will no longer be generated. A sealed enclosure prevents this undesirable acoustic short circuit, or air-pressure equalisation.

Possible solutions to the problem
Loudspeaker with partition, flush-mounted
Loudspeaker in closed housing

Apart from the technology – does the design of the speakers also play a part in agricultural machinery?

For our end-customers, in this case the farmers, it is important that loudspeakers are as inconspicuous as possible and do not intrude into the work area. This is why we offer a range of different grille types in different colours. With the grilles, it is also important to ensure that they are sturdy, but, at the same time, the thickness of the material is not too great. That is why our grilles are as wide-meshed as possible.

What sound system innovations in connection with agricultural machinery make VISATON stand out?

Normally, as in passenger cars, an amplifier is needed to connect the subwoofer to the radio. For agricultural machinery, we've developed a subwoofer that can be connected directly to the radio. This connection between the subwoofer and radio using a simple cable saves the customer considerable expense.

Improved safety while reversing

VISATON also ensures safety when reversing agricultural machinery. VISATON installs waterproof loudspeakers outside the vehicles to generate the beep sound during reversing to warn people in the vicinity of the machine. They are usually mounted in panels at the back of the vehicle, where they are not seen.

Let's have another look into the future. What trends and innovations are emerging in agricultural machinery sound systems?

The trend in driver's cabs is increasingly towards a central control unit with a touch display. Systems of this kind will replace external built-in radios in the future. This is why we at VISATON are currently developing an amplifier that will allow the loudspeakers to be connected directly to central control units of this kind.

Thank you for being so attentive.

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