It is difficult to ascertain the absolute loudness of typing noise by objective measurement. However, it may be practical to use such measurement to determine the loudness level difference in a comparison of the sounds from two typewriters. The requirements that must be met by an accurate measurement technique depend on the degree of accuracy required. Information pertaining to the accuracy necessary has been obtained by employment of two loudness matching procedures over a period of several months. The purpose of the tests was to determine the difference in sound pressure level of typing noise necessary to enable a person to identify reliably the louder of two typewriters operated simultaneously in a quiet background. It was found that under the conditions adopted for the investigation, differences in sound pressure level had to be nearly one decibel before they could be recognized 50 percent of the time. Characteristics of typing noise other than pressure level are discussed. The opinion is expressed that these will, in many cases, not cause significant measurement error, and that difference in loudness between typing noises can often be measured with practical accuracy by means of a sound level meter.