有可能用音響做到主動降噪嗎 - 特斯拉
By Faithe
at 2022-05-23T16:17
at 2022-05-23T16:17
Table of Contents
這類稱為主動噪音抑制系統(active noise control, ANC)
算是習知且成熟的技術
廣泛被應用於豪華車,或是對車輛NVH品質有特別要求的車輛
Silentium Active Acoustics on road noise
https://www.youtube.com/watch?v=5x9NEpfRZuc
https://i.imgur.com/lnbxQS5.jpg
主要原理如你所提,產生反向的波形抵銷
這套系統的優劣取決於產生的反向波形準確性和即時性
另外車輛的噪音來源分三大類:
1. 引擎 (engine noise)
2. 胎噪 (rolling noise)
3. 風切聲 (wind noise)
就ANC的抑制效果,引擎>胎噪>風切聲
簡單講變動程度越大或難以預測的噪音來源,ANC效果就越差
從noise spectrogram來看,引擎噪音的能量集中在特定的階次
https://i.imgur.com/sf9E69N.jpg
(ex: 引擎3000rpm時,50Hz就是1階,100Hz是2階)
由於引擎噪音的頻率跟轉速有關
只要得知當下轉速資訊,就能確認噪音波形以及產生特定頻率的反向波
https://i.imgur.com/KJOgpRC.jpg
也因此ANC在抑制引擎噪音的效果最好
引擎噪音可以透過引擎當下的轉速資訊預測
路面噪音則仰賴在感測器量測,比較不即時
https://i.imgur.com/CL3mXwL.jpg
變因也比較多
1. 輪胎:種類、花紋、胎壓
2. 路面條件:乾燥、潮濕、坑洞、柏油、水泥路等
但至少是車輛行進中持續會有的噪音,因此採用ANC的抑制效果也還不錯
Silentium Active Acoustics on road noise
https://www.youtube.com/watch?v=5x9NEpfRZuc
相較下風切聲來源更不固定(瞬間陣風等更難預測),且屬較高頻
抑制的效果最差
至於車內裝摩擦敲擊之類的異音(squeak & rattle)
因為過於隨機,所以基本上ANC無用武之地
有趣的是,雖然風切聲最難用ANC抑制
但風切聲屬於較高頻的噪音
透過氣密性、隔音棉就能有效解決問題
https://i.imgur.com/TzOBpEb.jpg
藍色是road nosie
紫色是wind noise
綠色是engine noise
橘色是high ordder powertrain noise(motor/pump)
可以看出引擎、馬達等轉動件噪音是相對明顯集中在特定頻率(好預測)
Active Sound Management In Cars
https://reurl.cc/andW69
Advanced, broad-band active noise cancellation now available in cars
https://reurl.cc/1Zb9YG
※ 引述《sxnz (OO)》之銘言:
: 是這樣啦
: 以model3為例
: 眾所皆知胎噪跟風切處理得沒很好
: 但以特斯拉引以為傲的軟體功能
: 利用麥克風收音
: 再利用車內音響產生抵銷用的聲波
: 這個是有可能可行的嗎
: -----
: Sent from JPTT on my iPhone
--
Tags:
特斯拉
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