What are some simple ways to reduce the amount of echo there is in a room? Phone calls sound terrible!?

Our new office is a large open space with 5 individual desks. It has high exposed ceilings with hardwood floors. Basically a large rectangle. Phone conversations sound like they are coming from the mens room - with echoing that can be heard even when holding the phone directly to onces mouth.

We've added some large office plants, lots of furniture, and even some small paintings but the echo is still terrible. Our next step would be to purchase a rug, but the cost is significant. What are some inexpensive ideas on how to reduce the echo?

I appreciate the answers - but here are some limitations:

1. No windows, it is an interior office.
2. No cubes - desks are all open sawhorse with glass top style
3. Cieling is unlikely the issue, exposed beams with insulation (insulation should suck up sound)
4. Hanging rugs would not meet professional requirements. We do have some canvas paintings, but they didn't do much.

Rugs seem to be the remaning consensus, but small rugs would not fit the decor. A large rug (20 feet at least) would fit the decor, but would cost $2K plus.

I heard a rumour that we only need to fix one wall to stop the sound - is that true?

Any other ideas?

Hang some fabric on your cubicles.
Hang drapes
Hang valances on the windows
Get some smaller rugs for throughout the office
Add pillows to a couple office chairs

Hang cloth artwork on the walls and from the ceiling. Carpet too if there isn't any.

Go find a used office furniture supplier and buy short (4') upholstered cubicles and place in the front and side of each desk. This will deaden the sound

Get some throw rugs

Are there draperies on the windows? How about soundproofing panels that are used in music studios?

I have a favourite restaurant that was just a concrete box when they opened and the noise was horrendous. They got about 4 large (2m x 2.5m) framed carpet \ thick material pieces and put them on the walls around the restaurant. It works like a charm.

Foam egg-crate material on the walls. It's essentially what they use in recording studios.

You could also check with a building materials recycler and find carpeting cheap.

PICTURES OR TAPESTRYS, MORE FURNITURE

Large floor pillows if you have no furniture.

It costs 30 - 40 % less to cork the cieling with drop cieling alternating cork tile, than to carpet, and you can keep the nice wooden floors.