Restoring an Old Recording

Clean an old recording of clicks, noise and hum, and leave an archive that can be traced back to the raw transfer.

Tool profile

Kind: guide
Vendor: 本站
Form: 流程
Platforms: 通用
Price: 不适用
Jobs: 流程
Verified: 2026-10-30

What you have to hand over

An archive-ready restoration: the raw transfer, the restored version, an access copy and a log of the processing chain. The restored file keeps the sample rate and bit depth of the transfer; transfer at 96 kHz and 24 bit to leave room for processing. If the carrier is already brittle, make a transfer copy before discussing cleaning. Deliver WAV plus a note describing the noise types, the order of treatment, how much reduction was used and any passage that could not be repaired. Keep the raw file separately and never overwrite it.

Three steps

Back up and transfer first. Clean the heads and tape path, confirm speed and azimuth, record a raw file with no processing, and generate a checksum. Second, work in stages: repair clicks and dropouts, then remove hum, then apply broadband denoising and gentle EQ. Third, compare: after every process, A/B against the raw. Keep a little noise rather than shave off the tails of voices or instruments. Write the order into the log so any step can be undone.

Tools and pages

A DAW and a spectral repair tool are enough. Read the site page Audio Restoration first, then the glossary entry Noise Floor. Remove hum with narrow notches on the fundamental and its main harmonics; mains frequency is 50 Hz in China and 60 Hz in the US, so measure before cutting. Denoise in two or three small passes, never one wide-open pass. Old recordings have little high end to begin with, so lift it with a broad, gentle shelf rather than a spike.

Acceptance checks

Clicks and pops are gone. The 50 or 60 Hz hum fundamental is lower without making voices or instruments dull. Denoising leaves no metallic edge or watery texture. Overall level is raised without clipping. The raw file and checksum are kept. The log can reproduce every step. Archive and access copies are named apart, with sample rate and bit depth stated.

Why work gets sent back

Only the restored file survives and the raw is lost. Denoising is pushed to the maximum and tails and breath disappear. The hum frequency is guessed and the hum remains. Repeated sample-rate conversion eats the high end. Heavy compression flattens the dynamics. No log exists, so nothing can be reproduced three months later. The restored file is treated as a master and clipped at release. Only a compressed access copy is delivered, which is not enough for an archive.

Listen in the library

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All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).

Sources

磁带转录、去嗡与降噪的处理顺序，依音频修复通识核查，未抄文本
原始文件留存、校验和与存档格式，依档案数字化通识核查，未抄文本

Used for fact-checking only; all prose is original.