Bob Backway

Sound may be described as the last frontier of realism for the model railroader. Yes, it is true that sound systems for model locos date back almost to the first powered models themselves. But it wasn't until the age of miniature electronics and digital sound that this aspect of modelling could be considered practical and realistic on the average layout. As prices are driven down by technological advances we can expect to see sound become the "norm" in our future models.

Another driving force is the introduction of new Command Control systems, particularly the NMRA's DCC Standard. These new systems have the ability to control more than a loco's speed and direction having several "Function" outputs just begging to control lights, animation and sound. DCC decoders share similar technology to digital sound modules. The logical combination of the two will result in economies of scale and price.

An otherwise "dead" layout is brought to life with the help of sound giving it a feeling that the train is running through an environment, not just a base board, plaster and ground foam. Sound can also fill in the gaps, the natural or man made world of the layout that could not be modelled for lack of time and space.

A real sound copied onto a device such as a tape recorder. With analog recording methods the information stored is subject to the degradation of the record/copying/play system and recording media. Analog sound can be used effectively on the layout but can't fit in a loco!

A sound made using electronic circuits. Usually a mix of primary sound generators followed by various envelope generators and filters attempting to manipulate the sound to imitate the original. Synthesis used to sound as good as vinyl did before CD's came along!

A real sound stored in a coded form by sampling the real thing. The sample is an accurately reproducible copy of the original within the limits of the reproduction system. Further copying does not degrade the sound quality.

• Ease of installation
• Good for exhibitions as can give the loudness required to compete with ambient noise levels
• Provides the best bass (low frequency) response for those that want a loco chuff to vibrate the walls
• Often suffer from repetitiveness and lack subtlety
• Best used for "atmosphere"
• Requires a sophisticated location system to simulate loco movement, that is the sound and the imagined creator often appear detached.
• The simplest of systems can be a home made tape recording of sound pertinent to the models environment. More sophisticated systems incorporate engine sounds and whistles either automatically controlled or incorporated into throttles.

• Ease of installation
• Much better than having one sound source. Allows intermediate sounds to come from their expected source alleviating the location problem. They can be easily controlled by events around the modelled source.
• Even better for exhibition layouts. Picture a steam loco blasting out of a tunnel to grab the onlookers attention.
• The use of digital sound has greatly improved the effect. For example a real recording of a ding dong gate is a vast improvement on the many synthesized units tried over the years.
• Reasonable speaker sizes are possible and so do not compromise quality.

• The simplest of systems consisted of a track transmitted steam sound connected to a speaker via a device to block the track power and a cam operated switch on an axle to turn the "chuff" on and off.
• Modern systems have digital sounds for every noise a loco can make. The modelled accuracy being as good as recordings of the actual prototype.
• The sounds come from their expected source - even when mobile.
• The necessity of small speaker sizes seriously limits loudness and frequency response (it is impossible to vibrate the walls with a diesel throb using such small speakers).
• Best for a home layout with low ambient noise levels.

• Spreads the realism by adding a "presence" to other than the loco bringing the whole train to life.
• Cattle sounds have been available for larger scales for some time.
• Rutger Friberg, a DCC group member, put a sound chip and moving dancers into a Marklin Ballroom car. Since then we've played with flange squeal, coupler clunk, train crew, passengers and animals.
• Command control or pulse control provides the power so no messing around with batteries and switches.

Entering the exhibition and the first thing you hear is a poorly synthesized ding dong "noise" coming from the other end of the hall. Sound is always around us but we unconsciously filter most of it out while having at the same time the ability to detect important sounds from within high noise levels. This complex capability of our ear must be kept in mind when modelling sound.

Sounds that are present intermittently in the background that add a "live" feeling to your layout. Ambient sounds should be heard only during quiet periods such as pauses in conversation or when particularly listened for.

Background sounds should be gentle, subliminal and non-repetitive. Even a busy part of the layout should "bustle" quietly.

Sounds that imply action and identify with an object on a layout. They should appear to come from or only be clearly heard in the vicinity of their modelled source.

An intermediate sound such as "ding dongs" should be heard during conversation but should not dominate the other end of a large layout.

Generally sounds emitting from the locos, after all they're what we're here for. They can also be scenario related sounds which give the layout purpose and flair.

A feature sound such as the loco at the centre of attention should be louder, but not too louder, than the intermediate sounds. If the overall effect is too loud you will soon annoy the viewers and drive the operators up the wall by the end of an exhibition.

Most of us have been to a scenery planning clinic where the use of guiding lines and scene division have been used to paint a picture or tell a story. The same concepts are as important when using sound. With sound it's best to place yourself as an observer on a nearby hill. Here you will only get a hint of sound from the scene spread before you. Sitting there you may here a mill saw start, a dog bark, a truck squeal to a halt. Each time you will look in that direction and expect to see what you heard, a mill, a house with a kennel or dog, paws up on the fence, a truck just stopped outside the general store.

This effect is important, but don't over do it. Whether you use a tape and switched speakers or digital effects you may like to try a sequencer. This is an electronic device that uses timers to space sounds in a certain order at a preset time interval.

"Loco enters night scene and whistles for road crossing, dog barks, wakes baby, dad swears at dog, light goes on and baby stops crying."

The whole sequence could be triggered by a track detector. The icing on the cake is to make the whole sequence occur only every 4 or 5 passes. This has two consequences. First the sequence is infrequent enough not to annoy and secondly when the viewer has finally convinced their partner to wait and listen, it won't happen!

Miniature speakers can be found in many consumer items from toys to audio equipment and home computers. Headphones in $2.00 shops provide a small speaker suitable for high pitched sounds such as chuff and whistle for a logging loco. Better quality headphones have larger speaker sizes and hence a wider frequency response. These are cheaper bought separately at an electronic parts shop such as Jaycar, Dick Smith or Tandy. Obsolete computer modem boards have the smallest speakers I've seen but they are rather inefficient.

Once you're into sound you find yourself collecting various speakers in your travels and will soon have samples of many shapes and sizes to experiment with. Various speakers have different parts of the frequency spectrum that they work best in. The only generalization being that normally the larger the diameter the lower the frequency response. They also vary in the amount of power they can take without distorting, or in extreme cases, dismantling themselves.

It pays to try a range of speakers temporarily installed in their final situation (see below re baffles etc) before making up your mind. The differences can be substantial.

Sometimes it may be necessary to "doctor" a speaker to fit it in a model. Any outer cover or mounting brackets that are not used can be cut off. The only important part is to ensure that the cone is supported in the voice coil. Sometimes the cone has to be cut to fit in the model. While lowering output and affecting frequency response, this can sometimes give a better result than using a smaller speaker. It is important however to make the cut sides a good fit in the "box" and run glue lightly along the edge so it is fixed to the box. Without the unattached area of cone flapping around the sound is cleaner.

Yes, you have to be rough sometimes!

All speakers convert electrical energy into sound waves by moving a surface, the cone in the case of a conventional speaker. The movement is greatly influenced and in fact enhanced by the speakers surrounding environment. To put it simply a speaker will perform better if the sound waves emerging from the front cannot be interfered with by those from the rear of the cone. Interference reduces the volume because the front and rear waves are opposite in phase and cancel each other when they meet. Ideally the surface through on a speaker mounts should be hard, flat and infinite in dimensions. Obviously we'll need to compromise! At least try and provide a hole through which the speaker transmits its energy. For example through a floor or a loco grill.

A speaker also works better if it's in an enclosure. This has an effect of reinforcing the sound, particularly the lower, bass, frequencies. Normally the enclosure size is calculated using the resonant frequency of the speaker, in a model it's do what you can. From cut down film canisters to utilizing blocked off sections of the model body. The simplest and crudest reinforcement is a piece of foam plastic jammed behind the speaker. An ideal situation is a speaker through the floor of a box car filled with dacron wadding.

Sealing the enclosure prevents out of phase sound waves from "leaking" out from the speakers rear.

All materials have a resonant frequency at which they vibrate when sound of that frequency is applied. Brass models, just like the brass section of the orchestra, make a sound appear "tinny". This is the biggest complaint of brass model owners who've used sound. Similarly plastic models can develop an annoying buzz.

The following tips help cure this problem:

• Reinforce your baffle, eg tender floor, by gluing thick styrene to it.
• Make sure the speaker is held firmly against the baffle. Try silicon for metals, it can be removed easily.
• Cover all interior surfaces affected by the rear of the speaker with some body deadening material (try heavy cloth, rubber, silicon or even lead). Make sure all surfaces are covered and firmly glued to the deadener.
• Seal all "air leaks" with silicon rubber.
• Plastic resonance can usually be fixed by stiffening with styrene.

Electrically speaking a sound unit is operating in a very noisy environment. With motor commutators nearby radiating radio frequency energy and noise spikes coming via track power from other locos by way of a delicate contact system.

If you have problems with noise try reducing it by using capacitors across your motor leads or the power leads of your sound unit. I keep a range of small ceramic capacitors from 100 picofarad to 0.1 microfarad for motors and 0.1 to 1000 microfarad for power supplies. The larger values are usually tantalum (small) or standard electrolytic capacitors and are polarised so remember to put the + end to the + wire of your power lead.

In general the smaller value capacitors get rid of radio frequency noise and electrolytics the lower frequency audio noise. For a power lead you may need protection for both ie a 0.1 and a 100 microfarad capacitor.

The common wires (called earth or ground) for all electrical units in your system should be kept separate from each other to a point as close as possible to where the ground first appears in the model. This prevents "earth loops", noise created in a device by large earth currents from another device.

We have seen how to improve the output from a speaker. Some of these tips can also be used to tailor the sound to suit a particular application. Placing plastic foam against a speaker tends to "kill" high frequencies and deepen a sound such as a chuff.

Projecting a speakers output through a tube can give it depth as well as ensure that all available energy is pointed in the direction of the listener. Tunnelling the sound is important in scenario planning

As user recordable sound modules become more common so will the use of computers to tailor sound. Computer programs are available that have all the capabilities of a major recording studio. The sound can be altered to cope with poor speakers, given depth and mixed, extended and enveloped without any loss of quality. A sound card or a direct digital connection can then "program" the sound module.

Sound quality is in the ears of the listener. Use the tips above to experiment and obtain the sound that you want.

• Digital steam & diesel
• Choice of US & European prototype
• 8 step diesel engine sound and many other loco sounds
• Real time whistle, horn and bell
• DC, DCC, radio control or stationary

Remote Control Systems

Box 1118 Bayswater Vic 3153

Tel/FAX (03) 9762 7785

Mobile 014 029 083

$US110+

Dallee Electronics Inc.

10 Witmer Rd, Depot C, Lancaster PA 17602

Phone: (717) 392 1705 FAX: (717) 392 4694

Internet: http://www.dallee.com

• Various digital US steam & diesel sounds

$US275

Watts' Train Shop

Phone: (317) 873 6524 FAX: (317) 873 6522

Internet: http://www.wattstrainshop.com

• Radio controlled throttle with many loco sounds

Speed, Direction & SOUND Inc.

Dept. NGG-97

1840 E Warner Road, Suite A105-260, Tempe, Arizona 85284

Phone: (602) 705 4544

Internet: http://www.members.aol.com/rgs455/sds.htm

• Sound and lighting decoders for DCC
• Under table sounds
• Motion activated onboard livestock sounds
• Sound chips interchangeable

$US130+

RRE, POB 1672 Highland, IN, 46322

Phone: (773) 202 9931

Internet: http://www.tttrains.com/rre

Email: realrail@aol.com

• Incorporated with a wireless throttle (infrared or radio)
• DCC on board combined decoder, light & sound available
• Many loco sound effects on board or under layout.
• Various US loco whistles available.

$130+

ThrottleUp!

555H Burbank Street, Broomfield, CO 80020

Phone: (303) 465 4435

FAX: (303) 465 4191

$US140+

Tony's Train Xchange

24 Corduroy Road Essex Jct, VT 05452

FAX: 802 878 7684

Internet: http://www.ttx-dcc.com

Email: info@ttx-dcc.com

• Various self controlled 4"x2.9"x1.8" modules having various background & intermediate sounds

$US65

QSIndustries

3800 SW Cedar Hills Blvd, Ste 224, Beaverton, OR 97005

Phone: 503 350 0595 FAX:503 626 9995

$79.95

The Signal Box

Shop 3/457 Great western Highway Faulcanbridge 2776

Phone: 02 4751 2088 FAX: 02 4751 4503