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.
Full Answer. Some checks, such as payroll checks, have a specific expiration date. In this case, how long the check is valid is written on the front of the check. For instance, a check that says only valid for 90 days from the date issued will expire 90 days from the date on the check. In some cases, the issuer of the check will send a new check at the recipient's request, but they are not required to do so.