Stevland Hardaway Morris (né Judkins; May 13, 1950), known professionally as Stevie Wonder, is an American singer-songwriter, who is credited as a pioneer and influence by musicians across a range of genres that include rhythm and blues, pop, soul, gospel, funk, and jazz. A virtual one-man band, Wonder's use of synthesizers and other electronic musical instruments during the 1970s reshaped the conventions of R&B. He also helped drive such genres into the album era, crafting his LPs as cohesive and consistent, in addition to socially conscious statements with complex compositions. Blind since shortly after his birth, Wonder was a child prodigy who signed with Motown's Tamla label at the age of 11, where he was given the professional name Little Stevie Wonder.
Released in late 1972, Wonder's album Talking Book featured the No. 1 hit "Superstition",[49] which is one of the most distinctive and famous examples of the sound of the Hohner Clavinet keyboard.[50] Talking Book also featured "You Are the Sunshine of My Life", which also peaked at No. 1. During the same time as the album's release, Wonder began touring with the Rolling Stones to alleviate the negative effects from pigeonholing as a result of being an R&B artist in America.[17] Wonder's touring with the Stones was also a factor behind the success of both "Superstition" and "You Are the Sunshine of My Life".[45][51] Between them, the two songs won three Grammy Awards.[52] On an episode of the children's television show Sesame Street that aired in April 1973,[53] Wonder and his band performed "Superstition", as well as an original called "Sesame Street Song", which demonstrated his abilities with television.
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Wonder is one of the most notable popular music figures of the second half of the 20th century. He is one of the most successful songwriters and musicians.[112] Virtually a one-man band during his peak years, his use of synthesizers and further electronic musical instruments during the 1970s helped expand the sound of R&B.[113] He is also credited as one of the artists who helped drive R&B into the album era, by crafting his LPs as cohesive, consistent statements with complex sounds.[113] His "classic period", which culminated in 1976, was marked by his funky keyboard style, personal control of production, and use of integrated series of songs to make concept albums. In 1979, Wonder used Computer Music Inc.'s early music sampler, the Melodian, on his soundtrack album Stevie Wonder's Journey Through "The Secret Life of Plants". This was his first digital recording and one of the earliest popular albums to use the technology, which Wonder used for all subsequent recordings.
Octave bands, a type of frequency band, are a convenient way to measure and describe the various frequencies that are part of a sound. A frequency band is said to be an octave in width when its upper band-edge frequency, f2, is twice the lower band-edge frequency, f1: f2 = 2 f1.
Each octave band is named for its center frequency (geometric mean), calculated as follows: fc = (f1f2)1/2, where fc = center frequency and f1 and f2 are the lower and upper frequency band limits, respectively. The center, lower, and upper frequencies for the commonly used octave bands are listed in Table II-1.
The width of a full octave band (its bandwidth) is equal to the upper band limit minus the lower band limit (bandwidth = f2 - f1). For more detailed frequency analysis, the octaves can be divided into one-third octave bands; however, this level of detail is not typically required for evaluation and control of workplace noise.
Electronic instruments called octave band analyzers (OBA) filter sound to measure the sound pressure (as dB) contributed by each octave band. These analyzers either attach to a type 1 sound level meter or are integral to the meter. Both the analyzers and sound level meters are discussed further in Section III.
Hearing bands are a third type of HPD (Figure 11) and are similar to earplugs, but with a stiff band that connects the portions that insert into a worker's ears. The band typically wraps around the back of the wearer's neck, though variations are available. Hearing bands come in a variety of sizes, shapes, and materials and are popular for their convenience. Hearing bands may not provide the same noise attenuation as properly fitting earplugs, as the portions that fit into the ears are stationary and cannot be twisted into place like earplugs.
Earplugs, earmuffs, or hearing bands alone might not provide sufficient protection from significantly high noise levels. In this case, workers should wear double hearing protection (e.g., earmuffs with earplugs). Avoid corded earplugs and hearing bands, as the cord/band would interfere with the muff seal.
Several sound-measuring instruments are available to CSHOs. These include sound level meters, noise dosimeters, and octave band analyzers. This section describes general equipment care, followed by the uses and limitations of each kind of instrument.
Octave band analyzers that are integrated into a sound level meter will be calibrated as part of the sound level meter. Detachable octave band analyzers must be returned to CTC for periodic calibration with the meter with which they are intended to be used.
Most sounds are not a pure tone but rather a mix of several frequencies. The frequency of a sound influences the extent to which different materials attenuate that sound. Knowing the component frequencies of the sound can help determine the materials and designs that will provide the greatest noise reduction. Therefore, octave band analyzers can be used to help determine the feasibility of controls for individual noise sources for abatement purposes and to evaluate whether hearing protectors provide adequate protection.
Octave band analyzers segment noise into its component parts. The standard octave band filter set provides filters with the following center frequencies: 16; 31.5; 63; 125; 250; 500; 1,000; 2,000; 4,000; 8,000; and 16,000 Hz. The special signature of a given noise can be obtained by taking SLM readings at each of these settings (assuming that the noise is fairly constant over time). The results may identify the octave bands that contain the majority of the total radiated sound power (Figure 19).
Sample bar chart screen: (A) selected frequency band (250 Hz ini example),(B) selected frequency in curve, (C) amplitude (dB) in band.Tabulation screen: lists amplitude in dB for each frequency band.
For octave band analysis, the ideal SLM network (weighting) scale setting is one that provides no weighting at all, such as the Z-weighted scale, which has an unweighted flat response across the entire frequency spectrum from 10 Hz to 20,000 Hz. The C-weighted scale is also an acceptable option for octave band analysis because, in the range of most workplace noise level measurements, unweighted sound level measurements are less than 1 dB higher than the corresponding C-scale measurements. The A-weighted scale, however, is not an appropriate setting for octave band analysis because, by definition, it influences the meter response differently at various frequencies in the range of normal human hearing.
For a more detailed analysis, the spectrum is sometimes measured in one-third octave bands. Although one-third octave bands can be useful for noise engineers concerned with precise frequency measurements, the standard single octave bands are sufficient for most evaluations performed by OSHA.
Whether detachable or integrated into a sound level meter, an octave band analyzer receives its daily calibration in conjunction with the sound level meter with which it will be used. This might involve activating an additional setting during the daily meter calibration. Consult the user's manual for the equipment you will be using.
The Type 1 SLMs used by OSHA (such as the Quest SoundPro) have built-in octave band analysis capability. Some other models of sound level meter are designed to work with a separate octave band analyzer that is physically attached to the meter (Figure 20). In either case, the sound level meter microphone operates normally, but the noise signal detected by the microphone is separated into its component frequencies. When the octave band analyzer is activated and a particular frequency band selected, the meter readout provides the decibel level associated with that frequency. By sequentially switching the meter to each frequency band and taking a reading, the CSHO can determine which octave bands contribute most to the noise.
In contrast, the following octave band analysis (Table III - 2) obtained during concrete demolition (multiple noise sources) indicated that many frequencies contributed to the noise level at that position -- a distance of 60 feet from the demolition point. At that point, the overall sound level was 91 dB, demonstrating a standard principle of sound: the sum of all octave bands is greater than any single octave band reading, but the logarithmic values cannot be summed by simple arithmetic addition. See Appendix B.3 for more information on determining the sum of two or more sound levels.
Some octave band analyzers can be set to automatic function (i.e., the instrument automatically checks the sound level of each frequency band and stores the results). Other instruments require the user to manually switch between the different frequency bands, recording each reading in sequence.
Variable frequency sounds and sounds that constantly vary in intensity present a challenge to frequency analysis. Unless the sound is relatively constant throughout the process of evaluating all frequency bands, it might not be possible to obtain an accurate reading. The CSHO should attempt to determine whether cyclic sounds have a stable period during which readings would be more accurate.
Increasingly, some SLMs can function as noise dosimeters (although they are larger than typical dosimeters), while many noise dosimeters provide instantaneous sound level readings in decibels and therefore can be used as Type 2 SLMs. Some models including the Casella dBadge2 and Svantek SV1041S can now be configured to have built-in octave band analyzers as well. 2ff7e9595c
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