tester.sh

#!/bin/bash
trap 'killall speaker-test; exit' INT

cat <<A
usage:    'j':  +10Hz
          'k':  -10Hz
          'J': -100Hz
          'K': +100Hz
A

F=200
while read -n1 A
do
    killall speaker-test
    case "$A" in
        j) let F+=10
            ;;
        J) let F+=100
            ;;
        k) let F-=10
            ;;
        K) let F-=100
            ;;
        *) break
    esac

    speaker-test -f$F -t sine &
    sleep .1
done