1. The ratio of the maximum reading to the minimum reading (the minimum often being the noise level) which can be recorded by and read from an instrument without change of scale. 2. The ability of a system to record very large and very small amplitude signals and subsequently recover them. The smallest recoverable signal is often taken to be the noise level of the system, and dynamic range as the ratio of the largest signal that can be recorded with no more than a fixed amount of distortion (often 1 to 3%) to the rms noise; see Figure D-29. However, sometimes signals that are buried in the noise can be extracted. The definition sometimes considers the entire signal extraction process rather than the recording equipment only. 3. For direct recording magnetic tape, the noise level is for unrecorded tape; bandwidth should be specified because selected narrow bandwidths may give improved dynamic range. The maximum range of standard magnetic tape is about 50 dB, of high output tape about 60 dB. 4. Instantaneous dynamic range or significance is the smallest signal that will cause a measurable change in the presence of a large signal. Word length imposes a limitation (14 bits represents about 84 dB).