A horn or trumpet gives a single carrying note, made from a hollowed animal horn, a conch shell or a pipe with a flared bell, and it is used for a few distinct counted blasts. Doubling its range needs about 4 times the sound power, so site the horn so the listeners are close and downwind, make the patterns count-based rather than duration-based, and keep the code short enough that a tired blower cannot confuse it.
Part of Signal Systems and Communication
Horns and trumpets are lip-blown instruments that give one loud, carrying note and are used for counted alarm patterns.
Range Costs Power, So Move The Listeners Closer
The parent article gives horn blasts as carrying 1 to 3 km depending on wind and terrain. The cost of range follows from the 6 dB per doubling rule of open air, which Noise Makers derives from 20 x log10 of the distance ratio.
Worked Example: What More Range Costs
- Doubling the range: 20 x log10(2) = 6.0 dB more at the source, which is 2 x 2 = 4 times the sound power.
- Tripling the range: 20 x log10(3) = 9.5 dB, which is 3 x 3 = 9 times the power.
- Going from 1 km to 3 km therefore needs nine times the power, a very different horn.
The assumption is open air with no wind, absorption or obstacles, so this is the least a longer range costs; real conditions cost more. The practical consequence is to move the listeners, not to build a bigger horn: place the signal horn where the settlement can hear it, and where possible so that the settlement lies downwind of the horn in the usual wind.
What You Need
- A horn. An animal horn cleaned and hollowed, with the tip cut off to form a mouthpiece, or a conch with its tip removed, or a pipe 2 to 3 cm across and 30 to 60 cm long with a funnel bell, as the parent article describes.
- A trained blower at each post. Lip-blown horns are a skill.
- A sheltered place to keep it dry and a spare.
- A written code (one table, shared with the flag and drum codes).
Method: Sounding A Reliable Horn Signal
Step 1: Count, do not time. A horn is hard to sound at an exact length when the blower is tired or frightened. The parent article’s “1 long blast (3 sec)” is a duration; define the pattern by count (one long, two short) and let “long” mean clearly longer than “short”.
Step 2: Leave a clear gap. Pause between blasts so the receiver can tell a repeat from a continuation.
Step 3: Repeat the whole pattern. A single pattern is easily missed or half heard. Sound it twice or three times.
Step 4: Acknowledge. The listener sounds back the acknowledgement. No answer means the alarm may not have been heard; send a runner.
Step 5: Tell horns apart. If two posts have horns of different pitch, the listener knows which one sounded without a code.
Diagnosing A Horn That Does Not Carry
- Cracked or leaking horn. Air escapes before it vibrates; seal or replace.
- Cold lips. In frost a blower cannot make a clean note; keep the mouthpiece warm.
- Wind from the wrong side. The sound is blown away from the listeners; move the horn or add a relay horn.
- Hills between horn and listener. Shade; add a post or relay.
Common Mistakes
- A long list of blasts. Under stress the blower forgets; the parent article’s code book already lists several horn patterns that overlap, so reduce them to a few that cannot be confused (see Simple Code Tables).
- Continuous blasting as an alarm. A person cannot blow continuously for long; the signal fails when the blower tires.
- One horn for the whole settlement. If the blower is taken or injured, there is no alarm.
Safety
Hearing, dizziness and mouthpieces
A horn sounded close to the ear can damage hearing. A blower who is breathing hard can feel faint; sit or kneel. Wash a shared mouthpiece between users.
What’s Next
- Learn next: Drums — lower sound that passes obstacles
- Combine with: Priority and Urgency Codes — which pattern outranks which