I have a bunch of audio files all sampled at 44100 Hz sample frequency. I am trying to remove all the frequencies which are outside the human hearing range (I use the following as reference: Frequency Range of Human Hearing, as well as robert.b's answer for determining the frequency value of a given bin: How to get Frequency from FFT result), and my basic approach is:

1. Perform an FFT on the files
2. Convert all frequency bin indices to actual frequencies
3. Remove those which are outside the range (i.e. below 20 and above 20,000 Hz)


Would that be a valid approach, and would it be possible to "put back" my signals to a state (using the inverse FFT) where I can play them and check if they still sound "normal"?


Question: Get phones on all members in a customer group
Answer: The easiest way (just example):

$phones = array();
foreach($customers as $customer)
{
    if($customer-&gt;getPhone())
        $phones[] = $customer-&gt;getPhone();
}


Because collection is object with objects (function _getItems() return array of objects, if i remember right).