dB(A) does not flag the presence of prominent tones.dB(A) levels does not correlate with perceived loudness for sounds with strong low-frequency content.dB(A) levels do not correlate reliably with perceived loudness for non-tonal sounds.dB(A) level differences give an indication of relative loudness for two sounds of similar spectral content, unless there is significant energy below 500 Hz.dB(A) levels correlate well with annoyance of certain types of transportation noise sources.dB(A) levels correlate well with hearing loss in industrial environments.The practical uses of dB(A) are very different from its original intent: The A-network strongly de-emphasizes sound energy below 500 Hz. The sound pressure level of a tone, after filtering by the appropriate network, was labeled dB(A), dB(B) or dB(C), and correlated decently with the perceived loudness. frequency for quiet sounds (the “A” network), speech-level sounds (the “B” network), and loud sounds (the “C” network). But for quieter sounds the difference was more dramatic than louder ones.īell Labs systematized their findings into three simple four-pole electrical networks that simulated the loudness response vs. One thing that was discovered was that low frequency tones of the same energy produced a smaller loudness sensation than the reference tone. Participants at the 1939 World’s Fair in NYC rated the loudness of tones of various frequencies relative to that of a 1 kHz tone. One area of interest was the perception of loudness.
In the 1930s Bell Laboratories was engaged in fundamental research on human hearing for application to telephone communications. That definition is overly optimistic and may lead to unpleasant surprises. Large amounts of alphanumeric data: sentences and paragraphs.DB(A) has come to be viewed as a convenient single number description of noise emission. The following table lists the data types available in desktop databases in Access 2010 and Access 2007. A complex lookup field allows you to store multiple values of the same data type in each row.ĭependent on the data type of the lookup field. A simple lookup field uses the contents of another table or a value list to validate the contents of a single value per row. When you choose this entry, a wizard starts to help you define either a simple or complex lookup field. The Lookup Wizard entry in the Data Type column in Design view is not actually a data type. Long Text, Number, Yes/No, and Date/Time should match their respective data types. Short Text data type result can have up to 243 characters. Note, the Calculated data type isn't available in MDB file formats.ĭependent on the data type of the Result Type property. You can designate different result data types from the expression. You can create an expression that uses data from one or more fields. Note, the Attachment data type isn't available in MDB file formats. You can attach files such as pictures, documents, spreadsheets, or charts each Attachment field can contain an unlimited number of attachments per record, up to the storage limit of the size of a database file. Up to 8,192 (each part of a Hyperlink data type can contain up to 2048 characters). Pictures, graphs, or other ActiveX objects from another Windows-based application.Ī link address to a document or file on the Internet, on an intranet, on a local area network (LAN), or on your local computer
Unique value generated by Access for each new record.īoolean (true/false) data Access stores the numeric value zero (0) for false, and -1 for true. Monetary data, stored with 4 decimal places of precision.
Up to about 1 gigabyte (GB), but controls to display a long text are limited to the first 64,000 characters.įor more information, see Using the Large Number data type.įor more information, see Using the Date/Time Extended data type. See The Memo data type is now called “Long Text” for more information on the Long Text details. Large amounts of alphanumeric data: sentences and paragraphs. The following table lists the data types available in desktop databases in Access 2013 and later versions.
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