February 6, 2017
As experimental physicists will verify, we live in a noisy world. There's a photo of Ernest Rutherford, puffing a cigar at the Cavendish Laboratory in conversation with John Ratcliffe under a sign reading, "Talk softly, please."[1-2] The sign was there to remind the normally loud Rutherford to refrain from adding the noise of his usual loud voice to the experimental data. You don't get a Nobel Prize in Physics by being timid.
Even the temperature-induced movement of atoms in a solid will spoil some experiments, so many experiments are conducted cryogenically at temperatures near absolute zero. The first detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) is a recent example of physicists overcoming environmental noise to make a significant discovery. Detection of such waves required measurement of a displacement a thousand times smaller than the proton radius.
To accomplish this, LIGO needed systems to dampen seismic noise. These were both "passive," involving elaborate mechanical mounting, and "active," using sensors and actuator circuitry. Since air molecules pinging the detection mirrors will also spoil sensitivity, LIGO operates in a vacuum. Creating this vacuum was no small feat, since the chamber volume is 10,000 cubic meters.
The range between a largest and smallest value is known as the dynamic range, with the "noise floor" representing the smallest value that can be sensed by an electronic system. It's hard for most electronics to match the dynamic range of human hearing and vision; or, the scent detection by many animals. Human vision functions from darkest night to brightest day, for a range of about 90 decibels (dB), and hearing operates over a 100 dB range.
The dynamic range of human hearing was taken into account when designing the compact disc (CD) digital audio system. The 16-bit encoding of compact discs gives a dynamic range of 96 dB (20log10(216)). This is quite an improvement over 1960s era magnetic tape recorders that were limited by noise to about 55 dB. This places a limit on the dynamic range of phonograph records of that era, since the music was recorded first on tape, although a vinyl phonograph record can have fundamentally about the same dynamic range as a compact disc.
When CDs were first introduced, some record producers tried to utilize their full dynamic range to disastrous result. My copy of Mike Oldfield's 1974 "The Orchestral Tubular Bells" is impossible to enjoy because of the large excursions in volume level. I could listen to this CD and some other music only when the dynamic range was compressed through some electronics of my own design (see photograph).
Dynamic range can be a problem in scientific measurement, and that's why our voltmeters and other instruments have range switches to match the instrument to the quantities being measured. While 16-bits are enough for music, the 16-bit Analog-to-digital converters for magnetic field measurement on the Van Allen Probes, launched in 2012 to study the Van Allen radiation belt, had automatic range switching to allow seven orders of magnitude of measurement (140 dB) within the 96 dB dynamic range.
Energy in our universe has a wide dynamic range. Photons of the cosmic microwave background radiation have a frequency of about 160 GHz, so their energy (E = hν = (6.63 x 10-34 joule-s)(1.6 x 1011 s-1)) is about 1 x 10-22 J. Ultra-high-energy cosmic rays have been detected with an energy of nearly 10 joules. The dynamic range of particle energy in the universe is thus 1023, or 460 dB!
While the dynamic range of magnetic tape recording was limited to about 55 dB, there was a method of extending the dynamic range of audio recording by a technique known as companding. A compander is a combination of a compressor and a complementary expander, with the dBx noise reduction system as a notable example. The dBx compressed audio onto magnetic tape in a 2:1 ratio; that is, it put 120 dB of signal into a 60 dB range. On playback, the 1:2 expansion recovered a 120 dB signal. The Dolby Type A noise reduction system had a similar action with additional circuitry that reduced processing artifacts.
- Z. Capri Anton, "Quips, Quotes and Quanta : An Anecdotal History of Physics," World Scientific Publishing Company, May 31, 2011, 252 pp., ISBN: 978-9814343473.
- Rutherford image at the Emilio Segre Visual Archives, American Physical Society, via Flickr.
- B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), "Observation of Gravitational Waves from a Binary Black Hole Merger," Phys. Rev. Lett., vol. 116, Document No. 061102, February 11, 2016, DOI:https://doi.org/10.1103/PhysRevLett.116.061102. Also available at arXiv.
- LIGO Technology, LIGO Laboratory, California Institute of Technology.
- NAB Magnetic Tape Recording and Reproducing Standards, Reel-To-Reel, Document E-416 (1965), Engineering Department, National Association of Broadcasters, PDF File via richardhess.com.
- B.B. Bauer and Arthur Kaiser, Gain Control Apparatus Providing Constant Gain Interval, US Patent No. 3,187,268, June 1, 1965.
- Arthur Kaiser and Emil Torick, "Compensated Platform Gain Control Apparatus, US Patent No. 3,260,957, July 12, 1966.
- Emil Torick and Arthur Kaiser, Control Circuit for Restricting Instantaneous Peak Levels in Audio Signals, US Patent No. 3,398,381, August 20, 1968.
- D.M. Gualtieri, "Build A Stereo Gain Controller," Nuts and Volts, January, 2012, pp. 28-33.
- Nicola Fox and James L. Burch, The Van Allen Probes Mission, Springer Science & Business Media, Jan 10, 2014, 647 pp.
Permanent Link to this article
Linked Keywords: Experimental physics; experimental physicist; noise; noisy; Ernest Rutherford; cigar; Cavendish Laboratory; John Ratcliffe; human voice; data; Nobel Prize in Physics; self-confidence; timid; temperature-induced; atom; solid; experiment; cryogenics; cryogenically; absolute zero; gravitational wave; Laser Interferometer Gravitational-Wave Observatory (LIGO); environment; displacement; proton radius; seismic noise; sensor; actuator; electronic circuit; circuitry; atmosphere of Earth; air; gas; molecule; mirror; vacuum; volume; cubic meter; electrical engineering; electrical engineer; Joseph Weber; United States Naval Academy; gravitational wave; resonance; resonant detection; Weber bar; aluminum cylinder; ringing; hertz; piezoelectricity; piezoelectric sensor; meters; Wikimedia Commons; dynamic range; noise floor; human hearing; visual perception; vision; odor; scent; animal; decibel (dB); compact disc (CD) digital audio system; 16-bit encoding; magnetic storage; tape recorder; gramophone record; phonograph record; vinyl phonograph record; record producer; Mike Oldfield; The Orchestral Tubular Bells; dynamic range compression; compress; audio engineer; audio engineering; CBS Laboratories; Nuts and Volts; hobby electronics magazine; metrology; scientific measurement; voltmeter; electric switch; analog-to-digital converter; magnetic field; Van Allen Probes; Van Allen radiation belt; orders of magnitude; energy; universe; photon; cosmic microwave background; electromagnetic radiation; radiation; frequency; GHz; Planck constant; joule; ultra-high-energy cosmic ray; George Washington; monochrome; oil painting; Gilbert Stuart (1755-1828); Crystal Bridges Museum of American Art; companding; dynamic range compression; compressor; dBx noise reduction system; Dolby Type A noise reduction system; B.B. Bauer and Arthur Kaiser, Gain Control Apparatus Providing Constant Gain Interval, US Patent No. 3,187,268, June 1, 1965; Arthur Kaiser and Emil Torick, "Compensated Platform Gain Control Apparatus, US Patent No. 3,260,957, July 12, 1966; Emil Torick and Arthur Kaiser, Control Circuit for Restricting Instantaneous Peak Levels in Audio Signals, US Patent No. 3,398,381, August 20, 1968.
Latest Books by Dev Gualtieri
Thanks to Cory Doctorow of BoingBoing for his favorable review of Secret Codes!
Blog Article Directory on a Single Page
- J. Robert Oppenheimer and Black Holes - April 24, 2017
- Modeling Leaf Mass - April 20, 2017
- Easter, Chicks and Eggs - April 13, 2017
- You, Robot - April 10, 2017
- Collisions - April 6, 2017
- Eugene Garfield (1925-2017) - April 3, 2017
- Old Fossils - March 30, 2017
- Levitation - March 27, 2017
- Soybean Graphene - March 23, 2017
- Income Inequality and Geometrical Frustration - March 20, 2017
- Wireless Power - March 16, 2017
- Trilobite Sex - March 13, 2017
- Freezing, Outside-In - March 9, 2017
- Ammonia Synthesis - March 6, 2017
- High Altitude Radiation - March 2, 2017
- C.N. Yang - February 27, 2017
- VOC Detection with Nanocrystals - February 23, 2017
- Molecular Fountains - February 20, 2017
- Jet Lag - February 16, 2017
- Highly Flexible Conductors - February 13, 2017
- Graphene Friction - February 9, 2017
- Dynamic Range - February 6, 2017
- Robert Boyle's To-Do List for Science - February 2, 2017
- Nanowire Ink - January 30, 2017
- Random Triangles - January 26, 2017
- Torricelli's law - January 23, 2017
- Magnetic Memory - January 19, 2017
- Graphene Putty - January 16, 2017
- Seahorse Genome - January 12, 2017
- Infinite c - January 9, 2017
- 150 Years of Transatlantic Telegraphy - January 5, 2017
- Cold Work on the Nanoscale - January 2, 2017
- Holidays 2016 - December 22, 2016
- Ballistics - December 19, 2016
- Salted Frogs - December 15, 2016
- Negative Thermal Expansion - December 12, 2016
- Verbal Cues and Stereotypes - December 8, 2016
- Capacitance Sensing - December 5, 2016
- Gallium Nitride Tribology - December 1, 2016
- Lunar Origin - November 27, 2016
- Pumpkin Propagation - November 24, 2016
- Math Anxiety - November 21, 2016
- Borophene - November 17, 2016
- Forced Innovation - November 14, 2016
- Combating Glare - November 10, 2016
- Solar Tilt and Planet Nine - November 7, 2016
- The Proton Size Problem - November 3, 2016
- Coffee Acoustics and Espresso Foam - October 31, 2016
- SnIP - An Inorganic Double Helix - October 27, 2016
- Seymour Papert (1928-2016) - October 24, 2016
- Mapping the Milky Way - October 20, 2016
- Electromagnetic Shielding - October 17, 2016
- The Lunacy of the Cows - October 13, 2016
- Random Coprimes and Pi - October 10, 2016
- James Cronin (1931-2016) - October 6, 2016
- The Ubiquitous Helix - October 3, 2016
- The Five-Second Rule - September 29, 2016
- Resistor Networks - September 26, 2016
- Brown Dwarfs - September 22, 2016
- Intrusion Rheology - September 19, 2016
- Falsifiability - September 15, 2016
- Fifth Force - September 12, 2016
- Renal Crystal Growth - September 8, 2016
- The Normality of Pi - September 5, 2016
- Metering Electrical Power - September 1, 2016
Deep Archive 2006-2008