172 SPECIAL SENSES. 



physical, as well as an aesthetic distinction between noise and 

 music. Taking, as examples, single sounds, a sound becomes 

 noise when the air is thrown into confused and irregular vi- 

 brations. A noise may be composed of a few musical sounds, 

 when these are not in accord with each other, and sounds 

 called musical are not always entirely free from discordant vi- 

 brations, as we shall see in studying musical sounds, properly 

 so called. A noise possesses intensity, varying with the am- 

 plitude of the vibrations, and it may have different qualities, 

 depending upon the form of its vibrations. We may call a 

 noise dull, sharp, ringing, metallic, hollow, etc., thus express- 

 ing qualities that are readily understood. In percussion of 

 the chest, the resonance is called vesicular, tympanitic, etc., 

 distinctions in quality that are quite important. A noise 

 may also be called sharp or low in pitch, as the rapid or slow 

 vibrations predominate, without answering the requirements 

 of musical sounds. These explanations, with the definition 

 that a noise is a sound that is not musical, will be better un- 

 derstood after we have described some of the characters of 

 musical vibrations. 



A pure and simple musical sound consists of vibrations 

 following each other at regular intervals, provided that the 

 succession of waves be not too slow or too rapid. When the 

 vibrations are too slow, we have an appreciable succession of 

 impulses, and the sound is not musical. When they are too 

 rapid, we recognize that the sound is excessively sharp, but 

 it is then painfully acute and has no pitch that can be accu- 

 rately determined by the auditory apparatus. Such sounds 

 may be occasionally employed in musical compositions, but, 

 in themselves, they are not strictly musical. 



In musical sounds, we recognize duration, intensity, pitch, 

 and quality. The duration depends simply upon the length 

 of time during which the vibrating body is thrown into 

 action. The intensity depends, as we have already stated, 

 upon the amplitude of the vibrations, and has no relation 

 whatsoever to pitch. Pitch depends absolutely upon the 



