Echo by the Morse code of beeps.

morse.sh

#!/usr/bin/env bash
#
# morsh.sh - Echo by the Morse code of beeps.
# Copyright (c) 2015 Koichi OKADA. All rights reserved.
# This script is distributed under the MIT license.
# http://www.opensource.org/licenses/mit-license.php
#

: ${freq:=10000}
: ${delay:=100}
: ${short:=50}
: ${long:=200}
: ${OPT_visualize}

if (( $# <= 0 )); then
  cat <<-EOD
	Usage: ${0##*/} <strings>
	  Echo by the Morse code of beep.
	
	Environment variables:
	  freq          : frequency [Hz]            (= $freq)
	  delay         : delay between signal [ms] (= $delay)
	  short         : short signal [ms]         (= $short)
	  long          : long signal [ms]          (= $long)
	  OPT_visualize : Visualize sequence of the Morse code
	                                            (= "${OPT_visualise}")
	EOD
  exit
fi

function gen_morse () # [ <char> ... ]
#   Generate sequence of the Morse code from characters.
# Return:
#   ${args[@]} : sequence of the Morse code.
{
  local i
  local sep=""
  args=()
  for i; do
    args+=( $sep )
    case "$i" in
      a) args+=( . _ ) ;;
      b) args+=( _ . . . ) ;;
      c) args+=( _ . _ . ) ;;
      d) args+=( _ . . ) ;;
      e) args+=( . ) ;;
      f) args+=( . . _ ) ;;
      g) args+=( _ _ . ) ;;
      h) args+=( . . . . ) ;;
      i) args+=( . . ) ;;
      j) args+=( . _ _ _ ) ;;
      k) args+=( _ . _ ) ;;
      l) args+=( . _ . .) ;;
      m) args+=( _ _ ) ;;
      n) args+=( _ . ) ;;
      o) args+=( _ _ _ ) ;;
      p) args+=( . _ _ . ) ;;
      q) args+=( _ _ . _ ) ;;
      r) args+=( . _ . ) ;;
      s) args+=( . . . ) ;;
      t) args+=( _ ) ;;
      u) args+=( . . _ ) ;;
      v) args+=( . . . _ ) ;;
      w) args+=( . _ _ ) ;;
      x) args+=( _ . . _ ) ;;
      y) args+=( _ . _ _ ) ;;
      z) args+=( _ _ . . ) ;;
      1) args+=( . _ _ _ _ ) ;;
      2) args+=( . . _ _ _ ) ;;
      3) args+=( . . . _ _ ) ;;
      4) args+=( . . . . _ ) ;;
      5) args+=( . . . . . ) ;;
      6) args+=( _ . . . . ) ;;
      7) args+=( _ _ . . . ) ;;
      8) args+=( _ _ _ . . ) ;;
      9) args+=( _ _ _ _ . ) ;;
      0) args+=( _ _ _ _ _ ) ;;
      .) args+=( . _ . _ . _ ) ;;
      ,) args+=( _ _ . . _ _ ) ;;
      \?) args+=( . . _ _ . . ) ;;
      !) args+=( _ . _ . _ _ ) ;;
      -) args+=( _ . . . . _ ) ;;
      /) args+=( _ _ . . _ . ) ;;
      @) args+=( . _ _ . _ . ) ;;
      \() args+=( _ . _ _ . ) ;;
      \)) args+=( _ . _ _ . _ ) ;;
      \ ) args+=( , , ) ;;
    esac
    sep=,
  done
}

function gen_beep () # [ <Morse code> ... ]
#   Generate arguments for beep command
#   from sequence of the Morse code.
# Arguments:
#   <mores code> : "," or "." or "_"
# Return:
#   ${args[@]} : arguments for beep command.
{
  local i
  local sep
  args=()
  for i; do
    args+=( $sep )
    case "$i" in
      ,) args+=( -f 1     -D $delay -l 0      ) ;;
      .) args+=( -f $freq -D $delay -l $short ) ;;
      _) args+=( -f $freq -D $delay -l $long  ) ;;
    esac
    sep=-n
  done
}

function split () # <strings>
#   Split strings to characters.
# Return:
#   Output to STDOUT for one charactor per line.
{
  awk '
    BEGIN {
      for(i = 1; i <= length(ARGV[1]); i++) {
        print substr(ARGV[1],i,1);
      }
    }
  ' "$1"
}

function visualize_morse () # [ <char> ... ]
#   Visualize sequence of the Morse code.
{
  local i args slpw slps slpl
  read slpw < <(awk "BEGIN{print ($delay*2     )/1000}")
  read slps < <(awk "BEGIN{print ($delay+$short)/1000}")
  read slpl < <(awk "BEGIN{print ($delay+$long )/1000}")

  for i; do
    echo -n "$i ("
    gen_morse "$i"
    for j in "${args[@]}"; do
      case "$j" in
        ,)                sleep $slpw ;;
        .) echo -n " $j"; sleep $slps ;;
        _) echo -n " $j"; sleep $slpl ;;
      esac
    done
    echo -n " ) "
  done
  echo
}

readarray -t chars < <(split "$@")
gen_morse "${chars[@]}"
morse=( "${args[@]}" )
gen_beep "${args[@]}"
[ -n "$DEBUG" ] && echo "${morse[@]}"
[ -n "$DEBUG" ] && echo "${args[@]}"
beep "${args[@]}" &
[ "$OPT_visualize" ] && visualize_morse "${chars[@]}"