touching each other. It thus yields one-dimensional information of the contact area. Neither inverse filtering nor EGG are sufficient to completely describe the complex 3-dimensional pattern of vocal fold movement, but can provide useful indirect evidence of that movement. Another way to conduct voice analysis is to look at voice characteristics. Some characteristics of voice are phonation, pitch, loudness, and rate. These characteristics can be used to evaluate a person's voice and can aid in the voice analysis process. Phonation is typically tested by looking at different types of data collected from a person such as words with long vowels, words with many phonemes, or just typical speech. A person's pitch can be evaluated by making the person produce the highest and lowest sounds they can, as well as sounds in between. A keyboard can be used to aid in this process. Loudness is valuable to look at because for certain people, loudness affects the way they produce certain sounds. Some people need to speak louder for certain phonemes in comparison to others just so they can produce them. This can be tested by asking the person to use the same amount of loudness while singing a scale. Rate is also important because it looks at how fast or slow a person speaks. Use in medicine A medical study of the voice can be, for instance, analysis of the voice of patients who have had a polyp removed from their vocal cords through an operation. Computerized methods can be used to assess such issues in an objective manner. An experienced voice therapist can quite reliably evaluate the voice, but this requires extensive training and is still subjective. Another active research topic in medical voice analysis is vocal loading evaluation. The vocal cords of a person who speaks for an extended time suffer from tiring—that is, the process of speaking exerts a load on the vocal cords and tires the tissue. Among professional voice users (e.g., teachers, sales people) this tiring can cause voice failures and sick leaves. Voice analysis has been studied as an objective means to evaluate such problems. Voice analysis was an important factor in the study of vocal cord paralysis. It effects different functions of the vocal cords, from speech to breathing and voice analysis is used to study the effectiveness of Thyroplasty (medialization thyroplasty) improvements on the vocal cords after the surgery. Traditional voice recording is