Frequency is measured in hertz (Hz). A person who has hearing within the normal range can hear sounds that have frequencies between 20 and 20,000 Hz. The most important sounds we hear every day are in the 250 to 6,000 Hz range.
An issue date was added, and cheques may not be valid a certain amount of time after issue. In the US and Canada a cheque is typically valid for six months after the date of issue, after which it is a stale-dated cheque, but this depends on where the cheque is drawn; in Australia this is typically fifteen months.
R.G., Cleveland. A: There is no federal banking law about stale checks that indicates checks with certain dates aren't good. Banks won't necessarily reject any check because of the date on it. It's a myth that banks won't accept checks more than six months old or that carry a future date. (This is why post-dating a check protects you from exactly nothing.) Banks accept or decline checks based on whether they think the check is good.