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This is a list of the fundamental frequencies in hertz (cycles per second) of the keys of a modern 88-key standard or 108-key extended piano in twelve-tone equal temperament, with the 49th key, the fifth A (called A 4), tuned to 440 Hz (referred to as A440). [1] [2] Every octave is made of twelve steps called semitones.
refresh rate of NTSC CRT televisions and standard refresh rate of computer monitors: 10 2: 100 Hz 100 Hz: Cyclic rate of a typical automobile engine at redline (equivalent to 6000 rpm) 261.626 Hz: Acoustic – the musical note middle C (C 4) 440 Hz: Acoustic – concert pitch (A above middle C; A 4), used for tuning musical instruments 716 Hz ...
For instance, 660 Hz / 440 Hz (a ratio of 3:2) constitutes a fifth, and 880 Hz / 440 Hz (2:1) an octave. Such intervals (termed "just") have a stability, or purity to their sound, when played simultaneously (assuming they are played using timbres with harmonic partials) because pure intervals do not waver or beat regularly.
Meanwhile, the electronic musical instrument standard called MIDI doesn't specifically designate pitch classes, but instead names pitches by counting from its lowest note: number 0 (C −1 ≈ 8.1758 Hz); up chromatically to its highest: number 127 (G 9 ≈ 12,544 Hz). (Although the MIDI standard is clear, the octaves actually played by any one ...
For example, 1280×1024 (5:4) or 1360×1024 (≈4:3) in 16 colours at 60 Hz, 1056×400 [14h] Text Mode (132×50 characters); 800×600 in 256 or 64k colours; and even as high as 1600×1200 (at a reduced 50 Hz scan rate) with a high-quality multisync monitor (or an otherwise non-standard 960×720 at 60 Hz on a lower-end one capable of high ...
On smaller CRT monitors (up to about 15 in or 38 cm), few people notice any discomfort between 60–72 Hz. On larger CRT monitors (17 in or 43 cm or larger), most people experience mild discomfort unless the refresh is set to 72 Hz or higher. A rate of 100 Hz is comfortable at almost any size. However, this does not apply to LCD monitors.
ISO/IEC 9995 Information technology — Keyboard layouts for text and office systems is an ISO/IEC standard series defining layout principles for computer keyboards. It does not define specific layouts but provides the base for national and industry standards which define such layouts.
The standard full-size (100%) computer alphanumeric keyboard typically uses 101 to 105 keys; keyboards integrated in laptop computers are typically less comprehensive. Virtual keyboards , which are mostly accessed via a touchscreen interface, have no physical switches and provide artificial audio and haptic feedback instead.