diff --git a/scripts/beep-charlie b/scripts/beep-charlie
index 45a44a6..5490c84 100755
--- a/scripts/beep-charlie
+++ b/scripts/beep-charlie
@@ -1,4 +1,7 @@
 #!/bin/sh
+
+lock=/tmp/.beep-lock
+test -f $lock && exit 1 || touch $lock
 head -c 8 /dev/urandom | \
    hexdump -v -e '/1 "%u\n"' | \
    awk '{ split("0,3,5,6,7,10,12",a,","); \
@@ -6,3 +9,4 @@ head -c 8 /dev/urandom | \
    printf("%08X\n", 60*sin(450*exp((a[$1 % 8]/12)*log(2))*i)) }' | \
    xxd -r -p | \
    aplay -c 1 -f S32_LE -r 48000 -D plug:default
+rm -f $lock
diff --git a/scripts/beep-wigfrid b/scripts/beep-wigfrid
index b0a42bf..5198ab2 100755
--- a/scripts/beep-wigfrid
+++ b/scripts/beep-wigfrid
@@ -1,4 +1,7 @@
 #!/bin/sh
+
+lock=/tmp/.beep-lock
+test -f $lock && exit 1 || touch $lock
 head -c 4 /dev/urandom | \
    hexdump -v -e '/1 "%u\n"' | \
    awk '{ split("0,3,5,6,7,10,12",a,","); \
@@ -6,3 +9,4 @@ head -c 4 /dev/urandom | \
    printf("%08X\n", 40*sin(450*exp((a[$1 % 8]/12)*log(2))*i)) }' | \
    xxd -r -p | \
    aplay -c 2 -f S16_LE -r 48000 -Dplug:hdmi1
+rm -f $lock