The PC speaker is normally meant to reproduce a square wave via only 2 levels of output (the speaker is driven by only two voltage levels, typically 0 V and 5 V).
For example, if your payments for March and July 2010 were each one month late, the report may continue to show (for seven years from the date after each payment was due) that you were 30 days late twice in 2010, even though the tradeline for that account also shows your payments for the rest of 2010 were made on time.
The late payment is added to your credit report when your payment is more than 30 days late. An entry is added to your credit report and can stay for seven years. If you miss the next payment, the entry is updated to 60 days, and so on until your account is charged-off after 180 days. Your credit score may drop.