# CHM阅读器专业版 vs sound

The clearest difference is review sentiment: sound at 100% against CHM阅读器专业版's 57%. sound also leads on in-app purchases (none vs 3). CHM阅读器专业版's advantage is update cadence (every 10 days vs every 4 months) and iOS requirement (15.6 vs 26.2). On price, ads and device support there is nothing between them.

Both are free to download. CHM阅读器专业版 sells 3 in-app purchases, starting at $1.99 per month. sound asks for nothing beyond the download.

CHM阅读器专业版 ships an update every 10 days, sound every 4 months. The most recent releases landed on October 24, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | CHM阅读器专业版 | sound |
| --- | --- | --- |
| Price | Free | Free |
| Positive reviews | 57.1% of reviews | **100.0% of reviews** |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 10 days** | Every 4 months |
| Monetization | Paid | **Free** |
| Size | 7 MB | 135 MB |
| Requires iOS | **15.6** | 26.2 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [宁伟 陈](https://appshunter.io/developer/1801975672) | [祖浪 吴](https://appshunter.io/developer/1883572387) |

## What reviewers say

### CHM阅读器专业版

[App page](https://appshunter.io/ios/app/chm/id6746235244)

Easily view CHM files on your iPhone or iPad. This professional reader supports opening documents from various sources, offers quick navigation via table of contents, and includes full-text search. Enjoy comfortable reading with Dark Mode support.

**Highlights:** Open CHM files from Files, Mail, Safari, Automatic table of contents parsing, Full-text search, Dark Mode support, View help documents and tech manuals

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 月度会员 | $1.99 | per month |
| 年度会员 | $9.99 | per year |
| 永久会员 | $12.99 | one-time |


### sound

[App page](https://appshunter.io/ios/app/sound-time/id6776622151)

This app helps you focus and learn with a Pomodoro timer and white noise generator. Track your progress with detailed statistics and enjoy a seamless experience with dark mode and dynamic island support.

**Highlights:** Pomodoro focus mode, Customizable timer and sound alerts, White noise sound library, Focus time statistics, Home screen widgets, Dark mode and Dynamic Island support

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is CHM阅读器专业版 free?

CHM阅读器专业版 is free to download, with in-app purchases available.

### Is sound free?

sound is free to download, with no in-app purchases.

### Do CHM阅读器专业版 or sound have ads?

Neither CHM阅读器专业版 nor sound shows ads.

### Which is updated more often, CHM阅读器专业版 or sound?

CHM阅读器专业版 ships an update every 10 days, and sound every 4 months. Most recently, CHM阅读器专业版 was updated on October 24, 2026 and sound on October 25, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*