5

For example, dial tone, DTMF, busy tone, ringing tone, etc.

  • 1
    There are obviously many instruments on which it's impossible to do this - whereas a synth could do it all day long. –  Mar 09 '22 at 09:02
  • @piiperiReinstateMonica Many answers are assuming that synthesizers are fair game; I suspect the OP might mean others. The "how" also could be taken many ways: I personally suspect they mean "please give me a table showing how the various tones are generated by combining pairs of pitches." But they might also mean something much more practical, like "What techniques will help me make, say, a violin replicate these sounds," like slow heavy bow. Or they might mean "Which instruments [presumably excluding synthesis] can get the closest approximation?" –  Mar 09 '22 at 18:02
  • I remember there was a guy in the 80s who could, apparently, hack a government system by whistling into a telephone. Not sure of the relevance, but it's there, somewhere. – n00dles Mar 10 '22 at 16:22
  • @n00dles There was a fictional character "Whistler" played by David Strathairn in the 1992 film Sneakers who was inspired by the real-life Josef Carl Engressia Jr., a.k.a. Joybubbles who was able to whistle 2600 hertz into a telephone. – Theodore Mar 10 '22 at 20:45
  • @Theodore I really want to watch that film now! – n00dles Mar 11 '22 at 20:13

3 Answers3

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The DTMF dial-tones are created by superimposing two sine waves at these frequencies (Wikipedia):

 Hz   1209  1336  1477

697     1     2     3
770     4     5     6
852     7     8     9
941     *     0     #

When you press e.g. key 4, two sine waves with frequencies 770 Hz and 1209 Hz are played. These frequencies don't exactly correspond to notes in concert pitch:

 697 Hz ~ F5  -  4 cent
 770 Hz ~ G5  - 31 cent
 852 Hz ~ G#5 + 44 cent
 941 Hz ~ A#5 + 16 cent

1209 Hz ~ D6  + 50 cent
1336 Hz ~ E6  + 23 cent
1477 Hz ~ F#6 -  3 cent

If you cannot use microtones, then a decent approximation would be:

       D6    E6    F#6

F5      1     2     3
G5      4     5     6
G#5     7     8     9
A#5     *     0     #

If you are using instruments capable of quarter-tones, you could raise G#5 and D6 by a quarter-tone. If you are confident that your players can produce more precise micro-tones, you could indicate the pitch offsets more precisely.

As for the tonal quality, DTMF tones are sine waves (albeit dirty sine waves because of telephone connections' low quality). When using concert instruments, flutes or clarinets played softly with a minimum of overtones would probably sound most realistic. When using electronics, use pure sine waves, maybe clip them slightly and add some white noise for more realism, and use a very abrupt attack and release.

Other signals such as the dial tone, ringing tone and busy tone, may differ per country, but the Bell System standard is (Wikipedia):

dial tone: 350 Hz + 440 Hz (continuous)
ring tone: 440 Hz + 480 Hz (2 seconds on, 4 seconds off)
busy tone: 480 Hz + 620 Hz (1/2 second on, 1/2 second off)

These tones correspond to:

 350 Hz ~ F4  +  4 cent
 440 Hz ~ A4  +  0
 480 hz ~ B4  - 49 cent
 620 Hz ~ D#5 -  6 cent

So an approximation would be:

dial tone: F4 + A4  (continuous)
ring tone: A4 + B4  (2 seconds on, 4 seconds off)
busy tone: B4 + D#5 (1/2 second on, 1/2 second off)

with the B4 a quarter-tone flat if possible.

In European countries that follow the ETSI standard, a single tone at 425 Hz (G#4 + 40 cent) is used for these signals:

dial tone: G#4 (continuous)
ring tone: G#4 (1 second on, 4 seconds off)
busy tone: G#4 (1/2 second on, 1/2 second off)

with the G#4 a quarter-tone sharp if possible. See Wikipedia for more details, and an overview of which countries don't (yet) fully adhere to the ETSI standard.

  • If sine waves are clipped, they should be clipped after mixing. – supercat Mar 09 '22 at 16:20
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    @Dekkadeci the difference between microtones and tuning errors is just intent and precision. Certainly wind instruments are capable of playing the same note at different pitches depending on the harmonic context. Given the right players, it ought to be possible to produce these frequencies fairly closely. –  Mar 09 '22 at 14:35
  • In UK, the ring tone is 2 rings, 3 rests, making 5/4 time. –  Mar 09 '22 at 11:23
  • @Tim is incorrect. The UK has a dual ring tone, but other European countries just use a single ring, as per the answer text. –  Mar 09 '22 at 10:33
  • "if you cannot use microtones": Flutes and clarinets are not restricted to equal temperament (nor to any other tuning system), since it's possible to vary the pitch of individual notes, but few humans (if any) are capable of the precision of frequency required to play a pitch of precisely (for example) 697 Hz. –  Mar 09 '22 at 08:48
  • @phoog - Expand microtone-reproducing capabilities to mis-tuned instruments and every single wind instrument you can find in a concert band and/or orchestra is capable of producing microtones (I should know from the snaps of "30 cents sharp" and "33 cents flat" I hear during tuning time). –  Mar 09 '22 at 13:33
  • I built a synth and used this info to create a touch-tone pad. The effects aren't perfect and, as the general assumption here is that the OP was asking about acoustic instruments and this answer is a good one, I won't post it as an answer, but here they are. – n00dles Mar 11 '22 at 20:20
1

It depends a lot on the instrument you're using. If you have a synth that can play sine waves at arbitrary frequencies, you simply look up the specs of these sounds and program the synth to play them. They're generally just one or two sine waves and maybe LFO frequency modulation. For authentic telephone sound, add quantization to 8-bit A-law and some noise.

If you don't have this kind of synthesizer, you're out of luck. The frequencies required are not really on any kind of musical scale. It's by design, so that any background noise would not be recognized as signal tones.

1

I doubt you'd get the result you want without using a synthesizer. Often times, these sounds are just two or three tones played at the same time.

For example, the Emergency Alert System (EAS) attention tone is made by playing 960 Hz and 853 Hz sine waves at the same time.