Areas where the noise limit values are exceeded on the Charente-Maritime (type C zones — LD type index) Prefectural Decree No 18-1536 of 24 July 2018

These maps also known as “type c cards” represent the parts of territories likely to contain buildings exceeding the limit values mentioned in Article L571-6 of the Environment Code and fixed by Article 7 of the Decree of 4 April 2006. Layer carried out by GIS workshop (April 2018) by compiling noise zones of type C related to road infrastructure (EREMA report on "Strategic noise maps of the department of Charente-Maritime (017) Large non-granted infrastructure; Deadline 3: 2017-2022) and motorway (“Non-technical summary of the sound environment mapping of the ASF network on the Charente Maritime department (17) in 2016”) For C-type maps (CBSTYPE), each noise zone is delimited by the lower limit isophone curve (Lden > 68 or 73, Ln > 62 or 65). For roads, the limit values correspond to a Lden of 68 dB(A) and an Ln of 62 dB(A). The noise level on a noise map is represented by regulatory indicators: the “Ln” (Level night) and the “Lden” (Level day-evening-night) which are harmonised indicators at European level. The Ln is the average noise level for the night period (22h-6h). The Lden is the 24-hour weighted average noise level to take into account the discomfort experienced, vis-à-vis the same noise level, greater in the evening and at night compared to the day.此类地图亦被称为“C型卡片（type c cards）”，其所指代的区域为可能存在超过《环境法典》第L571-6条及2006年4月4日政令第7条所规定限值的建筑的地块。 该图层由GIS工作组（2018年4月）编制，整合了与道路基础设施及高速公路相关的C型噪声区域数据，数据来源包括EREMA发布的《夏朗德-滨海省（017）战略噪声地图：大型未获批基础设施项目；第三阶段时限：2017-2022年》报告，以及2016年《ASF网络在夏朗德-滨海省（17）声环境制图非技术摘要》文档。 针对C型地图（CBSTYPE），每个噪声区域以下限等声级线（isophone curve）为边界，对应阈值条件为Lden＞68或73、Ln＞62或65。 针对道路基础设施，其限值标准为Lden=68dB(A)，Ln=62dB(A)。 噪声地图中的噪声水平通过欧盟统一协调的合规性指标进行表征：分别为夜间等效声级Ln（Level night）与昼夜等效声级Lden（Level day-evening-night）。 Ln指夜间时段（22时至次日6时）的平均等效噪声水平。 Lden则为兼顾晚间与夜间噪声相较日间对人体干扰更强的特性，经加权计算得到的24小时平均等效噪声水平。