EP0078130A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Automatic loudness controller
Assignee: CBS Broadcasting Inc
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Filing: 1982-10-13
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Granted: —
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Expires: 2002-10-13
Abstract
Abstract Broadcast apparatus for controlling the loudness level of program signals includes a variable gain device (14) for increasing or decreasing the level of incoming program material as a function of program loudness (using control 22) while simultaneously holding (by level control 24) the output level below a preset level to assure proper modulation levels and/or to prevent excessive reaction by peak limiters (not shown) which usually follow the loudness controller in the broadcast chain.
Inventors
- 👤 John C. Burne Iii
- 👤 Emil L. Torick
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 12:32
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3005; H03G9/00; H03G9/02
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
178 words
Apparatus for automatically controlling the level of audio frequency program signals to maintain uniform average loudness of sounds corresponding to said signals while simultaneously holding the signal level below a preset limit (TL, Fig.4), the apparatus comprising: variable gain means (14) connected to receive and adapted to amplify input audio frequency program signals and produce amplified signals; loudness analyzing means (22) operative responsively to said amplified signals for producing a first control .signal for controlling the gain of said variable gain means in accordance with loudness level of the program signals; and characterized by the further provision of signal level analyzing means (24) operative responsively to said amplified signals for producing a second control signal for controlling the gain of said variable gain means in accordance with the signal level and for limiting the amount of gain which can be contributed by said loudness analyzing means; and logic means (26) connected to receive and operative responsively to said first and second control signals variable gain means and for connecting the appropriate control signal to said variable gain means.
Claim 2
Dependent Claim
178 words
Apparatus for automatically controlling the level of audio frequency program signals to maintain uniform average loudness of sounds corresponding to said signals while simultaneously holding the signal level below a preset limit (TL, Fig.4), the apparatus comprising: variable gain means (14) connected to receive and adapted to amplify input audio frequency program signals and produce amplified signals; loudness analyzing means (22) operative responsively to said amplified signals for producing a first control .signal for controlling the gain of said variable gain means in accordance with loudness level of the program signals; and characterized by the further provision of signal level analyzing means (24) operative responsively to said amplified signals for producing a second control signal for controlling the gain of said variable gain means in accordance with the signal level and for limiting the amount of gain which can be contributed by said loudness analyzing means; and logic means (26) connected to receive and operative responsively to said first and second control signals variable gain means and for connecting the appropriate control signal to said variable gain means.
Claim 3
Dependent Claim
51 words
Apparatus according to clair. 1, wherein said apparatus further comprises: gain-hold means (20) coupled to said logic means (26) and connected to receive and operative responsively to the input signals for inhibiting gain increases by the variable gain means (14) during program signal lapses or periods of low-level background effects signals.
Claim 4
Dependent Claim
51 words
Apparatus according to clair. 1, wherein said apparatus further comprises: gain-hold means (20) coupled to said logic means (26) and connected to receive and operative responsively to the input signals for inhibiting gain increases by the variable gain means (14) during program signal lapses or periods of low-level background effects signals.
Claim 5
Dependent Claim
157 words
Apparatus according to claim 1 or 2, wherein the loudness analyzing means (22) comprises: a plurality of bandpass filters (30, Fig 2) all connected to receive the amplified signals (via 32) for separating the same into a like plurality of predetermined frequency bands; a like number of rectifying means (34) for individually rectifying the separated signals; a like number of detection means (34) for individually detecting and scaling the amplitude of the rectified signals to produce a transfer function proportional to an equal loudness contour (Fig.-3) over the range of loudness levels of sounds represented by the program signals; means (36) for arithmetically summing the scaled signals to produce a sum signal; and means (38) connected to receive and operative to shape the sum signal to cause the first control signal to conform the response of the apparatus, when under control of the first control signal, with the response of the human hearing process to impulsive sounds.
Claim 6
Dependent Claim
49 words
Apparatus according to claim 3, wherein the loudness analyzing means (22) has a transfer function proportional to a 70 phon equal loudness contour-representative of the loudness levels of broadcasting sounds as a function of frequency and intensity over a range of pressure levels from about 60db to about 80db.
Claim 7
Dependent Claim
54 words
Apparatus according to claim 3 or 4, wherein the filters separate the amplified signals into frequency bands of from about 50 to 250 Hz, 250 to 500 Hz, 500 to 1000 Hz, 1.0 to 1.7 KHz, 1.7 to 2.7 KHz, 2.7 to 4.4 KHz, 4.4 to 7.7 KHz and 7.7 to 15 KHz, respectively.
Claim 8
Dependent Claim
30 words
Apparatus according to any preceding claim, wherein the variable gain means (14) comprises a voltage controlled amplifier responsive to the first and second control signals for controlling the gain thereof.
Claim 9
Dependent Claim
46 words
Apparatus according to claim 3, 4 or 5, wherein the loudness analyzing means (22) further comprises circuit means (40 to 50) interposed between the summing means (36) and the signal shaping means (38) for establishing a threshold level above which the loudness analyzing means is operative.
Claim 10
Dependent Claim
95 words
Apparatus according to claim 7, wherein the signal shaping means (38) comprises a time constant circuit having a predetermined attack time (R52 X (C54 + C56)) and automatically selectable first and second release times dependent on the content of the program signals the first release time normally being relatively slow and the second release time being relatively fast for quickly increasing the amplitude of the first control signal and to thereby quickly increase the gain of the variable gain means (14) in response to a sudden drop in the loudness level of the program signals.
References Cited (Backward Citations)
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