Set the cpu frequency upon resuming from suspension?

Question

On Ubuntu 14.04, I hope to set the cpu frequency upon resuming from suspension, so I created a file /etc/pm/sleep.d/20_cpu_freq with content:

#!/bin/bash
case $1 in
        resume)
                sudo cpufreq-set -f 1.60GHz -c0
                sudo cpufreq-set -f 1.60GHz -c1
                ;;
        thaw)
                sudo cpufreq-set -f 1.60GHz -c0
                sudo cpufreq-set -f 1.60GHz -c1
                ;;
esac

But the cpu frequency isn't set upon waking up. What might be the reason?

Can I run sudo command in the script? Will that require me to type in the password of root?

Thanks!